The national broadcasting company presents Joel McCrae in Tales of the Texas Rangers Tonight transcribed from Hollywood another authentic re-enactment of a case from the files of the Texas Rangers Tales of the Texas Rangers starring Joel McCrae as Ranger Jayce Pearson Texas more than two hundred and sixty thousand square miles And 50 men will make up the most famous and oldest law enforcement body in North America Files of the Texas Rangers come these stories based on fact only names dates and places are fictitious for obvious reasons The events themselves are a matter of record case for tonight. No living witnesses It is 11 30 a.m. A Monday morning in November 1939 Sheriff Ross Betsby turns his car into a quiet residential street of Harper's Landing, Texas Seated in the car with him is mrs. Blackburn a medical assistant She becomes increasingly nervous as they approach a sign marking the home of dr. Walter Hennett Now don't go get and jump him is blackburn There could be a hundred reasons for the doc to be missing not doc him it and you know it It ain't like him to just disappear No sign of him since Saturday night wasn't a church yesterday and he ended his house this morning He's always there for visitor now is at 9 30 so he's probably out on a house call Maybe over to the hospital at Ridge Hill if he was the phone operator'd know about it Besides his car still in the garage. Well, here's a house better get out of the car and see if we can't raise it That's what I've been trying to do all morning Sure, he wasn't at church yesterday Of course, I'm sure he always gave me a ride home to my place And I'd always make Sunday breakfast for him before he'd start on his house calls You don't work for a man for ten years without learning his habits especially a doctor. Well, he's got to be around someplace Oh Hello, doc, you have a key miss blackburn never needed one before Front door the waiting room's always been open except at night. Of course. He could have driven off with somebody, but Well, I don't know If he's here, why doesn't he answer? Well, even doctors get sick and doc him. It's no young street might have had a stroke What are you gonna do Sheriff? We got to get inside I got no legal right to bust in without a warrant, but that'll take time and maybe this can't wait Why don't you just go in then doc knows you he'd understand. He doesn't understand I reckon he'll just have to sue me for a broken window I'll knock this in with my gun and I'll climb in and let you in through the door hurry Where's Doc's bedroom back here not here bed's been used though. It was all made up Saturday night when I left Then he slept here Saturday night bathroom door is open Nothing in there Reckon we better go through the rest of the house Kitchen's clear. You can see out back through the windows. There's nothing there either sure if I'm I'm frightened the sliding door to his office was closed when we come into the waiting room Better have a look at that office He isn't in here. I don't know Better stay back miss blackburn Dressed in a robe and pajamas Must had a heart attack come in here to get something for it and wait a minute. What is it? Only his robe It looks like blood to his blood from a bullet wound He's been murdered Sheriff vets be made an immediate request for the aid of a Texas Ranger Ranger Jase Pearson was assigned. He joined the sheriff at the home of dr. Hemmitt shortly after 1 p.m Jase it is miss blackburn. She was docked helper and this is Ranger Pearson miss blackburn Howdy, howdy, ma'am. I asked miss blackburn to stay until you got here Reckon she knows more about docking anybody. I gather you didn't live here in the house, ma'am. No, I Have my own place. I don't know just what I'd like to ask you yet until I look around Would you mind waiting a little longer stay as long as you need me? Thanks, ma'am Where's the body sheriff in the office through that sliding door? I've been keeping it closed off. Nobody's been in here but me and one deputy. He just took a couple of pictures Good I got a good examiner been here yet. No, but he'll be along soon. He's driving down from Hesterville Mark alongside the docks temple here and bruise about two inches long The pretty heavy blow looks like he might have been knocked out with a gun barrel that figures because he wasn't standing up When he was shot he was lying here on the floor what makes you think so bullet went right through the chest and buried in the Floor under him. I moved him a little and I dug the slug out here 45 yeah There's something funny about this though quite a bit of blood on this examination table almost six feet away from the body Yeah, I wanted about that myself the instrument tray and surgical dressings pulled up beside the table There's a couple of hypodermic needles that look like they've been used Well Jay's doc couldn't have been trying to treat his own wound He never moved after he was shot of that slug wouldn't have been in the floor right under him Of course he he might have staggered around before he was shot after he got hit on the head It's still wouldn't account for the blood on this table. There was no bleeding from the mark on his head That means the blood on the table come from somebody else medical examiner can type it for us later I want to see mrs. Blackburn for a minute Yeah We can use some help from you now mrs. Blackburn. I'll tell you anything I can Mrs. Blackburn was it part of your job to clean the doctor's office. Yes Every day after his final visit an hour according to the sign outside his evening hours were from 5 to 7 p.m That's right. You clean the place after 7 p.m. Saturday night. Yes What time did you leave? Well, doctor had a few calls to make after visiting hours house calls Awaited until he got back and fixed his dinner for him. I reckon it was late when I left after 10 o'clock Look through the door of the examination room for a minute Yes, sir. Is that surgical tray usually in that position? I mean did you leave it like that Saturday night? No Everything was put away in the cabinet. How about the examination table you clean that off Saturday night Yes, was the doctor expecting any patient after you left late? No, no He said he was going right to bed and he must have gone to J's the bed had been slipped in and you can see what it was Wearing I think it'd be all right for you to go home now ma'am if I need any more information we can reach you there Thank you. Tell the deputy outside that I said to drive you home like I just soon walk Yes, well, thanks for helping mrs. Blackburn Well, that settles one thing Jase doc had an unexpected patient late Saturday night somebody who routed him out of bed and killed him But why I got an idea it was to keep the doc from calling you keep him from calling me What do you mean whoever came here was hurt bleeding? So it wasn't a planned visit not somebody who came here deliberately to kill the doc Doc was killed to keep him from talking about the visit Oh doc Kammet had never talked about a patient's business only in one case where the law would require it He'd have to report it if he treated anybody for a bullet wound That's right Jase that could be it that probe on the instrument tray has blood on it And that's just what a doc could use to dig out a bullet. I know I've had a few dug out myself Let's comb this examination room again What are you looking for if we're right a slug doc him at dug out of his patient We found it wrapped in a piece of bloodstained gauze in one of the trash containers There was something else in the container to part of a faded blue denim shirt that had been used to bind the wound You must have been a bad wound Jase that denim was soaked. Yeah, take a look at this slug Looks like a slug from a savage 303, but doc was killed by a 45 That's natural the man who came here wounded was shot someplace else by somebody else wouldn't be the same gun Fellow we're after must have been in a gunfight thing the way it shapes up With all that blood he couldn't have come far couldn't have waited too long to get to a doctor and the chances are he wasn't alone Somebody must have been helping him.  I can't answer that one when the medical examiner gives us the wounded man's blood type I'm gonna send the two slugs we've got through the Austin for a ballistic check Get a rundown on every police report involving gunplay that took place anywhere within a hundred miles I hear on Saturday night The medical examiner came and after a quick check gave us the blood type of the man we were after I range for the two slugs We had to be sent through to Austin at the same time phone for a complete report on all shooting incidents that had occurred on Saturday night Then the sheriff and I started to drive to his office This looks like a tough one to me Jase We got a blood type to check for but I reckon a million people in Texas have type old blood Yeah, but not all of them are gonna have a recent bullet wound They can't account for you're right if we find one who's been wounded But for all we know the man doc treated might have got himself shot by accident if he did He wouldn't have killed the doc to keep him from reporting it. I guess you got me hugged hide on that point Jase but all the same I don't hold it a minute sheriff It's for me Unit 10 to KTXA.  Go on slope of Thunder Ridge Roebling County about 70 miles west your present location Time of death not yet determined waiting report of medical examiner Ten four is another unit assigned to that case This unit proceeding to join unit three to explore possibility of link between two killings Ten four Ten four unit 10 clear You think that might hook up with us Jase. It's the only thing that's turned up another range of units there unit three That's Steve Clark. We can work it together. Suppose.  It could still be a coincidence I know but it'll stop being a coincidence if he was killed by the same 45 that was used to murder doc Himmett I dropped the sheriff off then headed for Thunder Ridge when I got to the base I unloaded charcoal for my horse trailer and started the climb The sun was sinking as I started up the slope and darkness came fast I spotted torches moving like fireflies. I rode for them Easy easy charcoal watch your foot and boy Hello there That's you Steve Right coming up to you Howdy Steve. Howdy Jase got a walkie-talkie message. You were coming didn't come down the road to meet you because we wanted to get the Body out of here the medical examiner can't do much till we get it into town Where is the body back there in a pack mule with the sheriff's deputies? I'm leading the way down. I might as well get moving then I'll ride with you right all right. We're gonna move again Follow this gully all the way down and watch your step Come on. Come on. Charity Any line on how long he's been dead not for sure But I think it's gonna fit in with what you're looking for what I can judge he was killed Saturday night Got anything to back that up. Yeah, the man's a cowpoke works on that ranch at the base of the ridge He rode up here Saturday night to see some Mexican galleys been caught But he never did get back to the ranch after he left her shack I wonder why anybody traveled all the way up here to kill him He was ambushed on the way back to the ranch had been just as easy for the killer to wait until he hit the flat Down by the ranch funny you should say that why because he was shot down on the flat And how does body get up here and there's I can figure he started to ride back up to get help He wasn't killed right off fell out of the saddle and died where it fell seems to me He'd have ridden on to the ranch for help the ranch house is 11 miles off back up this way was only one mile Chase, I'll be able to show you the whole thing when we get down. I'll follow this tracks both ways Say you you leave your car near mine. Yeah Well, they shooting took place not far from where we parked There was a break in the fence there and the marks of a truck But they weren't deep enough to make a cast of them you mean whoever gunned him had a truck down there Yeah, that's right chase or say they're cattle tracks all over the place, too I might mean he surprised somebody who was trying to run some stock off the place Yeah, not only trying but succeeding a few widefaces that were grazing in that section can't be located It is fitting with your doctor killing depends on whether your cop oak was killed by a 45 And whether he returned fire and hit one of the many saw down there And he fought with them. All right, he was carrying a saddle rifle He dropped it when he got hit a wrecking. I found it beside his tracks down below Oh, he sent it on Austin only one thing you got to tell me then and I'll know if the two killings go hand-in-hand What kind of a rifle was the cop oak using what kind you're looking for jesh savage 303 you got a case That's what it was In just a moment we will continue with tales of the Texas Rangers starring Joel McCray as Ranger chase Pearson Three times mean good times on NBC. We're posting a little because here at NBC You'll find the roughest toughest most romantic crime fighters ever assembled under one network roof take Wednesday evening For example on Wednesdays you'll hear action with mr.. District Attorney the big story and that new daring private I Rex Saunders played by Rex Harrison. So just keep your mystery ear glued to your NBC station every Wednesday We continue now with tales of the Texas Rangers and tonight's case No living witnesses an authentic story from the files of the Texas Rangers The cowpauke and dr. Hammett had been killed by the same man All right, Ballistics proved the bullet dug out of the floor from under the doctor was a twin to the 45 taken out of the Murdered cowpauke Steve Clark and I put our horses in the double trailer. I was towing and headed for Harper's Landing Ballistic boys at the lab didn't take long comparing those slugs did they I never do it all fits even test fire the cowpaukes rifle It fired the slug doc Hammett took out of that patient. We're looking for we're not only looking for we're gonna find him And whoever was with him it must be more than one man. All right What you told me about the blood on that piece of denim shirt He couldn't have been in any condition to drive by himself not all the way to Harper's Landing 70 miles and he must have known he was gonna need a doctor Hey, you look like that gives you an idea it does I think it answers a question the sheriff asked me why they killed the doc instead of just tying him up and what's the answer They killed him because they didn't just happen by his place They knew doc Hammett and he knew them. That's a big conclusion Jason. It's not hard to reach either Look Steve doc Hammett's house in Harper's Landing isn't on the main street through town It's on a side street not easy to find in the middle of the night unless you knew where it was Not only that but they had to pass through two bigger towns on the way there towns with more than one doctor Steve if you were shot and wanted to keep it covered, but you had to be treated. What would you do? Well, go to my own family doctor reckon and hope that I could talk him into keeping it quiet You're right Jason. That means the men we're after must live in or near Harper's Landing Let's say on a ranch somewhere outside the town someplace they could have taken stolen cattle We know the brand mark and those stolen white faces say we're gonna do some range riding until we find them until they show up For sale at some commission house or auction barn You think the sheriff will be willing to ride with us. He will doc Hammett was a friend of his and the sheriff doesn't take to killers Carson ranch is about two mile farther on might stop there and get some grub if you'd like I'm all for it chef. How about it? Jay's haven't taken much eating time for the past two days Oh, why don't you just grab a handful of range grass? It's loaded with vitamins Hey, you'll be loaded with buckshot if you come up with any more ideas like that Yeah, come on Jay's for we get to skinny that a gust of wind will lift us right out of the saddle Okay, okay, I guess the horses can use a rest. You see there, chef. He don't care about us. Just the horses Look who's talking I never saw you sit down to a meal without seeing to it that your horse was fed and watered first I was only kidding Jayce. Let's get out of that Larson place. All right.  I Wish we'd find some sign of those white faces We must have looked over a couple of thousand head without finding a single all the brand And they got to be around Steve. They haven't been sold through any commission house or barn All records have been checked back through last Saturday. Yeah, we better find them soon for too many people know what we're doing Ranchers have seen us know we're not riding this range for exercise Yeah at the Larson ranch off there to the right of the Mesa there Nope, that place belongs to Auntie Covern and his son Jed. Yeah, pull up a minute Those cattle racking kind of funny Jayce Disturbing excited milling around can't see any reason for it wide open range No sign of a coyote or a mountain cat must be something they smell I've seen them act just that way when a beef has been slaughtered on the range blood smell stirs them up They start bunching just like that. No, nothing in that herd to interest us though, Jayce Can see none of them's white faces their white parts might have been painted over You know that kind of camouflage been used before I can't tell do we get close up? We're gonna have to check them sooner or later might as well be now. Well, there goes our lunch Steve Yeah, I guess they eat on the Cobra in place, too. Yeah, but the ants in Jed ain't exactly hospitable Well, come on get up boy. Yeah, and they're bunching right along Cobra and Spence line That's good.  Oh I'll hold the wattage. Thanks Climb through Sheriff, and I'll come through and hold it for Steve right Okay, Steve come ahead. Okay. I'm clear. Let it go. Ain't no strange stock here, Jayce They're all wearing Cobra's brand. Yeah, I can't spot any that have been altered. Besides, it's not a white face in the lot It's you that plane now What are they so head up about me it beats me What are you looking at Jayce tracks the way they've been milling around Marks form a big circle a boulder over there seems to be the middle of it They move up toward it, and they start to mill and pull back. Come on Wow, look at the Messer red ants around that boulder.  We'll get ants all over you Care about the ants so much. I just hope I don't get a miss a gopher teeth in my hand Feeling anything down there? Yeah Look quick line. Hey, Jayce. You better wash that off right away. I will you got your wire clippers sure What's the matter got the fence and bring the horses through we're gonna pull this boulder. Why Jayce?  Yeah, there wasn't something wrong with them They wouldn't have gone to the trouble of hiding them Pretty smart butcher in the stuff before they sold it probably figured every commission house in the state to be watching for brands They couldn't risk altering them and they couldn't risk keeping the stock around You've seen the Coburns lately sheriff haven't seen Jed for some time But I saw yancy only last night at the drugstore in town. Yeah, he buying something. Yeah, he was a lot of stuff Bandages adhesive tape. I saw the druggist wrapping it up sounds like the stuff they'd need to change dresses on a bad We're coming to their sheds house just the other side of right right into the sheds leave the horses there I don't want them to see these hides yet. Okay Take a look on that floor there jesh over there Yeah, one spot cleaned up mighty good. Look look at the beam right over it meat hooks little blood on them Yeah, I must have done his butchering right here made awful sure to get that floor clean. Let's go talk to them There's yancy now at the back screen door How do you have seen what you fellas want on my place the Rangers want to have a little talk with you I ain't got much time for talking. I got work to do. It's all we where's your son? I don't know. What do you mean? You don't know just like I said, I don't know Anything else that can help you with don't get smart yancy. You know where Jed is you better talk up He took yourself a little trip down to Mexico Suppose you invite us in and tell us all about it Rick and I don't have to heavy in if I don't want you sheriff He's perfectly right sheriff So Steve and I'll just wait here while you ride into town and get a warrant and we can invite ourselves in You want to make us do it the hard way and see I Ain't got nothing to hide one come in come in you keep a gun in the house Shotgun man the corner by the shoe about a 45 yet see never own one You haven't slaughtered any beef lately either. Have you? Any log in it nobody said there was Stashing the hides away under a boulder is a little bit unusual. You're getting kind of pale yancy. Are there ain't no What'd you stop for yancy? You're about to say there aren't any brand marks left on those hides, weren't you?  I told you he's not in Mexico. He's holed up some place recovering from a wound The wound doc him it was killed for treating. I don't know what you're talking about kidding here. Tell you Jays look at that ladder there in the corner Just a ladder. I was we're spiky to do some pink a man who's gonna paint usually buys some paint before he brings a ladder in What's that up in the ceiling looks like entry into the attic? That's better I'll hold this for safe keeping you might hurt somebody Keeping covered Steve. I'm gonna use that ladder and see what we got upstairs. I'll help you Jason Jed's probably up there, and he ain't kind of come quiet if he's corner Be smart Jed you can't get out of that attic.  They can't prove nothing. How about it Jed? All right But my leg is hurt You have to bring the light on to help me down. Sure. Just to make it friendly Open that trap all the way and drop your gun down here All right Yeah, that's better Set the ladder up again This is the gun we wanted Steve yeah 45 all right yet ease yourself down and I'll help you My leg hurts We didn't do nothing and that's all we ever gonna see we didn't do nothing here You love it up in Huntsville then it's full of innocent fellows just like you you ready Steve Yeah, Sheriff all said Jason good. All right, Yancy Jed get moving Throughout their trial Yancy and Jed coven steadfastly denied any crime however, Jed's blood type matched the blood found in the office of dr. Hemit and ballistic experts definitely identified his 45 caliber gun as the weapon used to murder both Dr Hemit and the cowboy whose body was found on Thunder Ridge It took the jury less than two hours to bring in a verdict of guilty The covens were sentenced to Huntsville Penitentiary for the rest of their natural lives And now here again is the start of our show Joel McCrae I believe you'll enjoy an amusing story I heard recently comes from a young lady who lives in the Lone Star State It seems that a Sunday school teacher was making quite an impression with the little ones in her class as she told How the pharaohs of early Egypt drove the children of Israel from that land a little fellow in the front row was biting His nails fiercely as the teacher went on to describe the cruelty's inflicted upon the Israelites How they were beaten and driven forth without food or water when the story was over the young fries stared straight ahead Finally he snapped gee whiz. Where were the Texas Rangers? See you next week folks. Good night Next week Joel McCrae in another authentic reenactment of a case from the files of the Texas Rangers Joel McCrae is currently seen starring in the Universal International Technicolor production Frenchy tonight's cast included Tony Barrett Virginia Greg Herb Ellis Ed Begley and Harley Bear This story was transcribed and adapted by Joel Mercott and the program was produced and directed by Stacey Keats Hal Gibney speaking Three times mean good times on NBC Turn back the calendar tomorrow evening The railroad hour takes you back to a golden bygone era with a refreshing presentation of the musical comedy high-button shoes Railroad hour singing star Gordon Macrae is joined by Margaret Whiting for this program and remember tomorrow You'll also hear a concert by the Boston Pops Orchestra Phil Baker invites you to join the $64 question next on NBC


Natural-based biomaterials are being used to develop new medical products for cutaneous injuries. These materials contain antioxidants that can support an expedite tissue regeneration. However, their low bioavailability limits their therapeutic activity at the injury site. To address this issue, researchers have integrated antioxidant compounds into the biomaterials to maintain their antioxidant activity while facilitating skin tissue recovery. Recent studies have demonstrated the potential of these biomaterials in promoting skin wound healing and tissue regeneration. Clinical trials are needed to further validate the efficacy of these biomaterials. Additionally, we provide an overview of the underlying mechanisms of reactive oxygen species, ROS, generation and discuss the use of ROS scavenging biomaterials in the literature. This article was authored by Nur-Isa M. D. Fadila, Sho-Jean Fang, Nur-Kazaya Kamaruzaman, and others. We are article.tv, links in the description below.


By taking the case of an E. coli, we estimated numbers of various proteins that are to be found inside the cell right. Some millions of proteins and billions of water molecules and small ions and so on and so forth. However, the thing to realize of course, is that these numbers are sort of whatever we found let us say there are some 10 to the power of 6 protein proteins and so on. Whatever numbers these numbers that we estimated these are sort of an average order of magnitude numbers. In reality the numbers of proteins if I think of a particular protein the number of copies of that protein inside the cell is sort of continuously changing right. And this is one such there is a figure that sort of tries to estimate that. So, this is colobacter this is a bacteria, there is the cell cycle of that. So, it is this total cell cycle from birth till cell division is around 150 minutes. So, 2 and half hours and these are the various phases of the cell cycle G 1 S phase and G 2 phase ok. So, what these people have done is that they have looked at clusters of proteins or clusters of M or any rather corresponding to various proteins that are active at different that are active and they see when these mRNAs or these DNA segments these are these genes basically they are active as a function of the cell cycle time ok. So, this curve over here is your cell cycle time from 0 to 150 minutes. Over here are these are different gene clusters and different gene clusters are responsible for different tasks. So, for example, cluster 1 might be replication cluster 2 might be biogenesis then there are clusters for chromosome segregation DNA replication and so on and so forth. And these colors represent 2 is when they are upregulated sorry this yellow is when they are upregulated blue is when they are down regulated. So, what you can see is that not all of these are sort of upregulated or active at the same time of the cell cycle. For example, this cluster over here clusters 8 and 9 these are sort of active towards the end of the cell cycle not so much towards the beginning whereas, these clusters are sort of active towards the initial phase of the cell cycle not so much towards the end and depending you can then say that which clusters are active when. So, for example, this one is active towards the initial part of the cell cycle this chromosome segregation which happens when the cell is dividing that is active towards the end of the cell cycle when the cell division of course, is absolutely at the end and so on. So, if you basically if you classify genes according to their functions of cluster genes or RNA or proteins whatever you classify them according to their function they are not always on they are not always produced the numbers fluctuate as the cell goes through its cell cycle depending on the function of that particular protein. And this is something that one must keep in mind that if I say that there are 1000 copies it does not mean that the cell has 1000 copies of that protein throughout that cell cycle. In some case in some during some time of the cell cycle it might during some time of the cell cycle it might be completely absent. So, that is one sort of thing to show that the cell is in constant flux things are constantly changing inside the cell. Therefore, one must look at kinetics of these things protein concentrations and so on in order to see what effects these have on the cell cycle. So, that is number one protein. So, mRNAs another thing for example, is this cytoskeleton. So, again we have talked about microtubules and actins this is again an electron micrograph showing that the green filaments over here are the microtubules the red spots are these actin filaments the blue is the nucleus that is not worry about, but these actin this cytoskeleton filaments the actins and the microtubules they are extremely dynamic. They polymerize and they depolymerize the rate of polymerization or the rate of depolymerization may depend again on the state of the cell cycle itself. For example, microtubules when the cell is dividing it assembles to form the spindle pole and it pulls apart the chromosomes and so on. So, again we look at these how to deal with this dynamic instability of these cytoskeleton filaments the fact that they are constantly in a state of flux they are polymerizing, depolymerizing over the next few lectures. So, just to remind this was the structure of the microtubules if you remember micro the basic subunit are these tubulin dimers alpha tubulin and a beta tubulin because there is a structural asymmetry we can assign a plus n then a minus n. So, this the one where it nucleates from this microtubule organizing center microtubule organizing center that is the minus n generally and then you have this microtubule going out of there. So, the microtubule consists of 13 filaments like this called proto filaments each proto filament is made up of these alpha beta tubulin subunits and when they polymerize they polymerize like this when they depolymerize they look slightly different the structure is slightly different it sort of played out and you can see this hopefully this will play again. So, if you look at these microtubules they are they are going some are going to be growing some are going to be shrinking and they are going constantly going to switch from a growth phase to a shrinking phase. And like I said this is very important in the case of the spindle formation I am sorry the picture is not very clear not even over there. So, these yellow things are your chromosomes which are going to be pulled apart these green lines are the microtubules which originate from the spindle pole the structure is like this here you have your two spindle poles your microtubules originate like this and here are your chromosomes the microtubules come and attach and then the pull the two copies of the chromosomes towards the two poles. If you look at the lengths as a function of time coming. So, if you look at the microtubule length as a function of time you can see that it grows for some time. So, the length grows and then suddenly it undergoes depolymerization. So, the length sort of drops very close to zero and again it will grow and again it will drop at some time. So, this process of switching from growth. So, this is the growth phase the growth of the polymerization this is the depolymerization this is the switching is called the catastrophe is called the catastrophe. And this switching from the depolymerization back to the growth phase is called a rescue is called a rescue. If you look at this curve which I cannot. So, the length scales of these are very different. So, for example, growth typically happens over time period of the order of minutes time period of the order of minutes. So, if you look at this curve these lines if they continue they would be the growth phase roughly 2 minutes 3 minutes is what the growth phase corresponds to. Whereas, this fall this depolymerization that happens very quickly over the order of a few seconds. So, if you look at this length of this microtubule as a function of time this is definitely not something that I would call in equilibrium the length as a function of time is not something that is sort of roughly constant it is constantly undergoing this sort of a flux between a growth and a catastrophe phase. And again we will try to look at how to sort of model this sort of dynamics where you have this polymerization depolymerization and switching between them. The same thing happens also for actins. So, the same thing happens. So, this is an actin polymer. So, the actin again has these subunits which are called the G actin the globular actin they come and bind to this actin filament.  So, this act so, this process in microtubules is called dynamic instability. This process of growth and shrinkage is called dynamic instability in microtubules in microtubules whereas, in actins where you have these this actin filament and you have addition at one end and from the other end the minus end it sort of falls off. So, this is called treadmilling. So, this is called actin treadmilling the monomers add at one end and it falls off the other end. And this is various consequences. So, for example, if you looked at this slide it does it means what is so, these are active processes in that they require energy. So, it refers to the state of whether it is an ATP whether the subunits have an ATP attached to them. So, whether they are hydrolyzed or not. So, whether it is an ATP state or ADP state. So, that is true actually even in microtubules there you have GTP and GDP. So, if you will see so, these are microtubules right. So, when subunits are being added they have they are this in this GTP state the triphosphate and then once they are added they actually the GTP converts to GDP. So, when they are being added they are being added in the GTP state then once they are added they convert to this GDP state. And that is why when it falls off actually the thing that comes out is GDP beta tubular. So, there is an internal state because this is an active process there is an internal state and that is true also in the case of actin there is this ATP to ADP conversion which is why you see those as different colors over there. I am trying to avoid that slide for the time being. Here this curve has now come. So, this was the catastrophe and the rescue. So, these are experimental plots of this microtubule length as a function of time. Ok. So, just to show what effect does this polymerization depolymerization have. So, this is actually a cell it is a skin cell from a fish if I remember correctly and this is moving. So, if you zoom in and if you look at this. So, what happens in this leaving edge is that there are these actin filaments and then there are molecular motors that move on these actin filaments. These actin filaments push against this cell membrane making the cell membrane sort of extend in this way and sort of. So, this is the top view of this cell, this is the side view of this cell. So, they extend these what are called these lamellopodia and then they sort of crawl along the cell surface. So, in this leading edge of this cell there are these highly dense networks of actin monomers. So, these are . So, this is again a active process through an interplay of these myosin motors and these actin filaments and the polymerization of these actin filaments. The same phenomenon ok, since we are on this slide anyway let me just show you that. So, this what comes over here is yellow and then slowly as the ATP becomes ADP you will see that it becomes blue over here. So, the state changes and now let me figure out how this is another example of how actin polymerization can help things move. So, this is an illustration of a bacteria Listeria which has invaded a cell. So, it is a infectious bacteria. So, which has invaded a cell what it does is that it takes over the actin polymerization machinery of the cell and it uses that machinery to sort of move around inside the cell. So, let me try to see. So, here is the bacteria, these blue things that you see are these actin filaments and as these actin filaments polymerize they sort of produce a force that pushes the bacterium like this ok. And what you are seeing over here are the in this red is marked as these actin, this green is marked as this bacterium cell. So, this actin polymerization provides a force that should sort of pushes this bacteria along and this is what is known as an actin comet and again we look at this in a little more detail when we look at actin and microtubules in the subsequent classes. So, you have subunits being added over here that provides a force that sort of propels this bacteria forward. So, this is the same thing these are just snapshots of that movie. If you look at these actin filaments there is a high density of filaments near the bacteria there is a low density of filaments. So, which are these longer lip filaments as you move further and further away from the bacteria. Your filaments so, which are these longer lip filaments as you move further and further away from the bacteria.


Good afternoon everybody. I hope you have finished your lab and you are back to your classrooms to listen to this lecture. Incidentally, before I begin the proceedings I would like to tell you that yesterday the director of IIT Bombay, the vice chancellor of Amruta University and our chief guest S. Ramadurai were very appreciative, not only of the workshop holding per se, but of the great enthusiasm that is being shown by all the participants. So I wanted to thank you all personally. Today we are assembled here to listen to one more exciting talk on security, which is generally considered an independent, standalone body of important knowledge, which is often thought as an advanced elective. We want to look at how we could integrate it in the university curriculum. I am very happy to see my colleague. So let me invite Professor Bernard Menazis. Let me introduce him very briefly. Professor Bernard Menazis is a professor of Department of Computer Science and among several things he specializes in the network security, although he has a very large spectrum of knowledge under his command. To tell you his background briefly, like many of us, he is also an alumnus of IIT Bombay. He went to the US to University of Maryland, Texas Austin, and after PhD he worked there for some time. He came back to India and he did a very remarkable thing. In a small college in Mumbai, he took up the challenge of setting up the Department of Computer Science, worked there for three years, brought that department to fairly good status, and then I could sort of invite him to join us here. He joined the then school of IIT with us, and which is now Department of Computer Science. He has recently written a book, I think it is just 2010 publication, Network Security and Cryptography. An excellent book, I have just perused it, but I will be reading it at great length. Why I am showing you this book is that the contents in this book were written not when he was working in the US, but on the basis of the work that he carried out here in India after joining IIT Bombay. We are very proud of this and several other works that he has been doing, and I think we are all fortunate that he agreed to spare half an hour to tell you in nutshell something important about this aspect of integrating security with the university curriculum. So, Banna, thanks once again and all yours. Thank you, Professor Fatuk for that very generous introduction. I think I did talk a little bit to the participants who came here around I think it was October or so for the one week program. I assume I am talking to them and many, many more around the country. So, I will just introduce what I would like to say in today's short lecture of about half an hour. The topic is integrating security into the university curriculum challenges and successes. So, when I joined Crescent which was actually founded by Professor Fatuk in 1999, one of the things that I really found most remarkable was the breadth of courses that we had in this new department. I think I could not find anything like that anywhere else in the world. Things like network security, e-commerce, mobile computing, data mining, many of these terms were the terms I was hearing for the first time in my life. And the e-commerce course had a strong security component in it. So, that is where this journey of writing this book and my interest in security actually started roughly 10 years ago. And at that time I hardly knew what the word cryptography even meant. But gradually because we got very good students, I supervised some of their seminars and theses and so on and so forth. This thing started to blossom and there was a time about a couple of years ago, say five years ago, we had started teaching a course per say on network security in around 2003. There was a half semester course and many of the students were extremely interested and requested us to make it a one semester course. They said there was too much material for just one semester and then from a one semester course it became a two semester course. And it has been growing ever since. There was a point where some people in a ministry asked us whether we could have an MTech in just security. So, the field is actually so important and so vast and ever growing that it's really a big challenge to write a book and to conduct courses in this area. So, what I basically want to talk about is the theme, how do we integrate security into the curriculum? It seems now as I look at syllabi in different universities in the country, I notice that security is already started to integrate itself probably as one course, probably as two courses. That is probably a compulsory courses in some universities and or an elective at the final year in some other universities. So, let me just briefly talk a little bit about security. There is so much on this in the news, one hears about all these kinds of attacks, mass fishing attacks, identity theft, distributed denial of service and just denial of service, distributed version of it. Malware, different forms of malware such as worms and viruses, spyware, botanists, Trojans, etc., etc. And of course, information warfare. Those of you who have been hearing the news may have a chance to read an article about the new Stuxnet worm, which is supposed to disable certain nuclear reactors in the world. So this area is becoming more and more sophisticated in the last couple of years and last couple of months in particular. So from attacks, we may ask ourselves what is it that causes some of these attacks? So when you introduce security, there are four different themes. The first is what are the goals of an attacker or a hacker? Then what are the attacks themselves? So I have just briefly mentioned some of these attacks, but an entire course on security would talk in depth about each of these attacks. And more importantly about the vulnerabilities or the reasons why these attacks occur in the first place. And then obviously how do you defend against these various attacks? So why do we have to study vulnerabilities? Once we know our weaknesses, they cease to do us any harm. Somebody said this several centuries ago and this is very very true today. So we need to know what are the weaknesses in our system, in our procedures and so on and so forth. So the key word over here is the word vulnerability. A vulnerability is a weakness or a lacuna in a policy. So it need not be hardware or software, it could be in a policy, it could be in a procedure, it could be in a networking protocol, etc. Within an organization that has the potential to cause loss or harm. And what are these vulnerabilities due to a variety of reasons? They range from sloppy software, things like the buffer overflow vulnerability. Many of you might have heard of SQL injection, cross-site scripting and so on and so forth in many of the web applications. So vulnerabilities may be due to one of the most important sloppy software protocol flaws in various standard protocols like TCP, IP, ARP, ICMP, etc. They could be due to system or application configuration. You can configure the registry wrongly, for example, you configure user's rights and group rights incorrectly, etc. And most important the kinds of attacks that cause phishing problems are human gullibility. So human weaknesses that is they just click on arbitrary email messages that they get on attachments to arbitrary email messages and so on and so forth. And that leads to serious problems. So these are the kinds of vulnerabilities one encounters. Once again, a course on security should do justice to this by talking about all these vulnerabilities which are basically the causes for these attacks. And then of course, once we've talked about the attacks, the causes of these attacks, the last and perhaps most important problem is to talk about defenses. And defenses range from things like prevention. There are so many different techniques that you can employ to prevent these attacks and those range from access control, authentication, encryption and so on. So a large part of the course will actually talk about many of these, namely encryption, authentication, etc. From prevention to detection, there are different detection techniques. There are different detection ideas over here in IDSS. For example, you can have host-based IDSS. You can have network-based IDSS. You can have signature-based IDSS. You can have anomaly-based IDSS. This is one area of security that overlaps with machine learning and data mining, for example. And then another mitigation strategy is traceback and forensics and also recovery. So when the attack has actually happened, how do you recover from it? How do you trace back the perpetrators of the attack and so on? So over the years in developing this course, as this course evolved, there were different ways in which these courses can be constructed. So I thought I would just tell you a little bit about the course structures. There are two possible ways, at least two possible ways. One is a cryptography-only course. Cryptography has become so important. It has become so interesting to many of our students that it is possible that we have a cryptography-only course. And then another course that deals with the other aspects of security such as cryptographic protocols, software vulnerabilities, malware, firewalls, etc. So that could be a second course. Alternatively, we could have two courses, a basic course and a follow-up course that exists in some universities, for example. So this is what we have experimented with and it has been fairly successful in IIT Bombay. And that is a first-level course, possibly compulsory, a course on network security and cryptography. So here the question is what exactly is network security? Does cryptography come under network security? What is the difference between network security and computer security or system security or language security and so on and so forth? So actually all of these could come under computer security. But the network security component which incidentally also includes cryptography is so very vast that it is sort of relevant to just use a term network security. It is also the more common or the more popular term. Just call it network security and let it under this roof, let everything else come under it. So a first-level course on network security and cryptography, followed by a more advanced course which could be a final year BTEC course or BE course which could also be a first-level graduate course on security. So a two-level, a two-series course program on security, a basic one and an advanced one. So let me just tell you some of the content of the first one and some of the content of the second one. Suggested material for a first-level course. The basic definitions, concepts and principles, things like authentication, non-repudiation and so on would come under the basic concepts. Then again the easier parts of cryptography, the early ciphers, secret key cryptography like the data encryption standards, the most well-known public key cryptography standard namely RSA, the cryptographic hash which is an important pillar of e-security, the discrete logarithm and various applications of it such as the Diffie-Hellman key exchange, L-Gamal signatures, L-Gamal encryption and so on and of course the public key infrastructure. That could be followed by cryptographic protocols or the so-called security protocols and we have some of the most well-known ones that you use when you typically go online and try to do e-commerce or you try to buy things on the net or you try to reserve airline tickets or railway tickets and so on, the SSL protocol. So before you actually hit the SSL protocol, it is a good idea to start with some fundamental design issues of security protocols, then go on to standard and very important man-in-the-middle attacks and replay attacks, the needom showed up protocol and the Kerberos protocol that is used in several Windows products for example and then finally the SSL protocol also called TLS. To continue the first course, then comes software vulnerabilities, the most celebrated of which are the buffer overflow vulnerability, cross-site scripting and SQL injection and then various mitigation strategies for these software vulnerabilities. Then as I mentioned before besides vulnerabilities in security protocols, even in regular protocols that have nothing to do with security, there are vulnerabilities. So it would be very important to investigate some of these in TCP, IP, etc. Followed by access control which you have at two levels at the operating system and inside the network. In the operating system, both in Linux as well as in Windows, you have different types of access control and the main types are something called MAC which stands for mandatory access control, DAC which stands for discretionary access control and RBAC which is role-based access control. So all of these are implemented in modern-day operating systems. And then finally malware, so an important treatment of various case studies of malware of different worms such as maybe Code Red and Slammer of email viruses which are so common like Melissa for example or So Big, various botnets like the Storm botnet, the Configure botnet that was very much talked about in the press about two years ago. So all of these things could come under the first level course. And the book that Professor Fartuck introduced which is the book that I just written actually talks about all of these topics and then. The first course could be followed by an optional elective second course, even the first could be an optional course but the second one would be a little bit more advanced. So in cryptography now one can go from RSA to for example ECC, Elliptic Curve Cryptography. One could go from desk data encryption standard to advanced encryption standard. You can look at different kinds of attacks on the secret key cryptographic schemes like differential and linear cryptanalysis and then something that has just been just come up in the recent past a few years ago something called identity-based cryptography which does away with digital certificates for example. From that we could go on to more advanced protocols like the IPsec protocol which is used in many VPNs that is virtual private networks and then of course this whole area of wireless security that is so important which spans wireless LANs for example which lands cell phone security that is 2G and 3G security and Bluetooth which you use also in many cell phones. So that is another important area wireless security which could be covered in the second course. Then once again more advanced topic in software vulnerabilities things like the format string attack which is a little bit more difficult to comprehend a second generation cross-site scripting attacks. This is one of the most important vulnerabilities in web application software today. So what are these cross-site scripting vulnerabilities and the more advanced versions of them also heap overflow attacks besides regular stack overflow attacks. One could also look at a variety of applications for example security and cloud computing electronic passports RFIDs electronic payment systems web services security and so on and so forth. So many of these are dealt with in the last few chapters of this book and finally you can choose your advanced topics for example security enhanced Linux. This is quite a fancy access control methodology over here in SE Linux which is a different paradigm compared to what you have in windows for example. You can look at more advanced and difficult topics like polymorphic malware detection there are many research papers in some of the leading universities in the world on this. So all of that could be integrated in a second level advanced course. Professor Fatak has just introduced this book to you so this is what the cover of the book looks like. There are about 25 chapters in all of these topics namely cryptography security protocols malware software vulnerabilities and so on and so forth. And these are some of the comments people have. So as I said before this course in IIT began in the year 2003 or so and it was a half semester course and I used to recommend one or two different textbooks as we went along. But over the years it seemed like we were covering less and less of the textbook and more and more of papers in various journals and various conferences and all across the internet. So I decided when I used to prescribe any book the students would complain and say that whatever I thought was not in the book so why are they purchasing the book?  So that forced me to start thinking of writing notes and this book emerged from the notes that I created. So the first thing is I tried to make it as comprehensive as possible. So it's a comprehensive text and that's what pretty much everyone tells me. I also try to include as many figures, tables, examples and case studies as I could. So a summary of all of this is at the back of the book, the back cover of the book. Many people, actually the publishers, they would like to see multiple choice questions and also me providing answers at the end of each chapter. So I did oblige them and at the end of each chapter I have about 7 to 8 objective type questions multiple choice questions with answers. So the student having read it can just check whether he's understood things and so on and if he's not understood he can go to the relevant parts and read it again. Then I thought I should include some very nice juicy questions at the end of each chapter. So besides the objective questions there are thought provoking exercises. Some of them are straightforward but some of them require quite a bit of thinking. So there are also programming assignments at the end of each chapter. So nice experiments, programming assignments, thought provoking exercises and so on and copious references and a detailed bibliography right at the end. And I'd like to conclude now before I throw the floor open to any questions to a very nice saying about security. So we are all accustomed to doing various things in engineering but security engineering is very different from the other kinds of engineering that you have been associated with. Let's look at this interesting quote here. Security engineering especially in this third wave requires you to think differently. Why? You need to figure out not how something works but how something can be made not to work.  Remember Satan's computer constantly trying to new ways to subvert it. So you need to have that kind of a mind, a very strange kind of mind when you're a security expert. You have to consider all ways your system can fail. You have to look at it this side and that side. You have to consider all ways your system can fail. Most of them having nothing to do whatsoever with the design itself. You have to look at everything backwards, upside down and sideways. You have to think like an alien. So this is a quote by a very famous security analyst by the name of Bruce Schneier. So with that I conclude my presentation and if you have any questions I'll be happy to answer them. So the question is on heap overflow. So the problem statement is buffer overflow actually. That's the attack, buffer overflow. There are two types of buffer overflow. One is called the stack overflow and the other is called heap overflow. What is the difference between the two? All your local variables in the program. So think of a program that you're writing. You have two types of variables. You have the so-called local programs, local variables or automatic variables. Those are placed on the stack and then you have the dynamically assigned variables, dynamically allocated variables. Those are placed on the heap. Now it turns out that the earliest buffer overflow attacks were those that were stack based. And there are different types of stack overflow attacks. There is the simple one where you actually put the shell code. The malcode that is part of the worm is actually called shell code. So you put the shell code on the stack. But the buffer overflow problem is the most marvelous example of which illustrates the race between the attacker and the defender. So the attacker tried to do this and then the defender defended against malcode on the stack. The attacker went one step further. He didn't have to put malcode on the stack. He used one of the C library functions. So there's an advanced C library as everybody knows which includes printf and so on. And he used one of those functions which is known as system. And by doing this he obviated the need for having malcode on the stack. So what the defender did was that he made the stack non-executable. The attacker went one step ahead and used the C library. It's a celebrated attack known as the return into libc attack and so on and so forth. So there were other defenses and then the attacker went one step ahead and so on. At some point in time the attacker started to look at heap overflow where dynamic variables are stored. And I have an entire section in the book on heap overflow. So you can see it's basically buffer overflow. You can overflow the heap and you can write into a block. That's allocated maybe to some other program. You can read and write from a block that's allocated to some other program. So if a password of somebody for example was stored on the other block you could be reading from that block and you could read that person's password for example. So this is an example of a heap overflow attack. And of course there have been defenses and it's entirely possible that in some of the operating systems the defenses work but they could be still insecure in some other operating systems. So that's another big challenge in software vulnerabilities. It could be possible that in some window systems the attack will work but in later versions of windows it may not work. On some Linux releases like Ubuntu version 7.0 something it might work. In version 9.1 it may not work and so on and so forth. So this is a wonderful thing for your students to actually try out. Our students here have tried it out. They have tried all these attacks, buffer overflow attacks at least 5 or 6 varieties of them on various operating systems. And they have actually showed and demonstrated that some of these attacks will work on some operating systems, some versions of operating systems yet not on others. So the question is about identity based cryptography. What is all this about? So it turns out that in the mid 1980s or so a guy called Shamir the same Shamir as an RSA Rivest Shamir Adelman the same Shamir came up with an idea called identity based encryption. Now what that means is basically it's the you know what's the idea of a public key and the corresponding private key. Now the question is why do you require somebody else's public key for a variety of reasons. For example if the other party wants to send you a session key he will encrypt it with your public key. So he would like to know what is your public key. So how do you communicate your public key to somebody else or how does somebody send you his public key. The celebrated way of doing that is through a digital certificate because a digital certificate is the binding between a person's identity or a person's credentials on the one hand and the person's public key. And this is sacred because it is signed it's digitally signed by a so called CA or certification authority. Now the whole business of creating these certificates disseminating them revoking them and so on and so forth is actually a costly affair for that you have something called the PKI a public key infrastructure. So using Shammi's idea that was later on developed in the 1990s and in the and about 10 years ago there were all sorts of new schemes that came up to make this a practical idea to make identity based encryption a practical idea. Whereby so here is the key idea your public key can be computed by anybody which is a function of some unique credential of yours. So what is this unique credential that almost all of us have it's the email address. Almost everybody's email address belongs to him and nobody else. If I have an email address like Bernard at it.itb.ac.in I can almost certainly guarantee you that no other individual has the same email address. Likewise the same thing with you ask anybody around whether somebody has the same email address as you have and almost certainly they will say this is the unique email address that only you have. So if that's unique to you then how about if we use the following idea as a function of that email address I can compute a public key. What does that mean all that it means is to get your public key I just need to know your email address. Of course I know your email address because I'm sending you email all the time and as a function of that email address there's a definite function which can be computed there are APIs to compute that function using that function. I can from your email address deduce your public key. So now I don't need to create certificates disseminate these certificates and have an entire infrastructure dedicated to this. So this is the idea of identity based cryptography. There has been a lot of work in the recent past lot of great ideas and very intense mathematics behind identity based cryptography. The so-called while pairing and tate pairings and so on and so forth. So if you're interested in more of the stuff there is one section in a book on identity based cryptography. But this is definitely a material for an advanced course and you can get I can furnish you with many references for the subject. So how are text based encryption techniques and image based compression is it compression or encryption? Encryption techniques different. So the techniques that we study namely secret key cryptography and public key cryptography assume that the underlying structure the underlying data is all binary. All that you need to use des or AES or RSA or ECC is basically a bunch of bits. So doesn't really matter whether those bits come out of images or whether those bits come out of text. It's the same thing and they are all very secure schemes. Now if you're trying to encrypt text using some very elementary schemes such as the Caesar cipher and so on then of course those schemes are useless. You can very easily launch various attacks on those schemes. However if you're using RSA or you're using ECC or des or AES then so long as you've got binary data all of these schemes should be very secure. So whether you use text whether the underlying data is text or whether it's images or video or whatever it should be pretty much the same thing. As far as video is concerned as far as wireless is concerned there are certain encryption schemes that are particularly amenable to those and those are for example stream ciphers. So whenever you're talking about wireless LANs for example the kind of cipher that you use would be a stream cipher like for example RC4. However there have been many attacks on RC4 some of which are explained in the text and some of which you can find on the internet like the well-known FMS attack. So there are these two classes of ciphers these days which are block ciphers and stream ciphers and typically you would want to use block ciphers for running text. And if you've got images and videos you could use stream ciphers such as RC4. So the question is what is differential cryptanalysis what is linear cryptanalysis what is cryptanalysis in general. So around I believe it was 1987 or so there were various schemes various what are called cryptanalytic schemes that came up in the context of DES. So DES was a scheme that was designed way back in the 60s and was continued to run quite well until the beginning of these cryptanalytic attacks. That are actually very sophisticated in nature. And around the mid 90s or early 90s to mid 90s there was a team in Japan for example that pioneered this technique called linear cryptanalysis. And there were some other scientists from Israel and so on that pioneered the technique of differential cryptanalysis. So let me tell you about one of them which is simpler to understand and that is linear cryptanalysis. Ask yourself what is the most important component of a secret key cipher. There are various components in a secret key cipher and by far the most important is something called the S box which is a substitution box. So what the substitution box does is it defines a mapping between a block of plain text and a block of cipher text. These are not the only things that are used in a regular secret key cipher but this is one of the different components. Now the most important thing about an S box is that it should be non-linear. If it is linear there are various ways to show that you can attack this S box. So what we do in linear cryptanalysis is we investigate the linearity or the non-linearity of different S boxes and we try to come up with an expression relating bits of plain text, bits of cipher text and bits of the encryption key. So that is this idea of linear cryptanalysis. And differential cryptanalysis is another technique which is slightly different which looks at a block of plain text, another block of plain text, the differences between these two blocks of plain text and the corresponding cipher text and the differences between the corresponding cipher text and then tries to deduce what is the original encryption key. So these are rather advanced techniques which are best left to an advanced course. And I think I have an entire section, I think I have done it in as much detail as you probably need to an entire section on the subject of linear cryptanalysis. There are some very interesting programming assignments that can be created for your class on linear cryptanalysis or for that matter on differential cryptanalysis. How to defend against DOS attacks? So this is a very interesting question. So I am very happy to see all these very very interesting thought provoking questions out here. How do you defend against a DOS attack? So this is something I just read somewhere a few days ago that you now have these kids that little kids and others are actually getting and they can launch DOS attacks. So what is a DOS attack? A DOS attack is a denial of service attack and it is caused by sending packets to a particular so packets from various places geographically dispersed places to a particular server. So that poor server gets so many packets it cannot service all of them and most of these packets are not real packets from clients but from attackers. So the poor server is busy servicing all these fake packets all these attack packets and cannot do its own work. It is being interrupted all the time. Now how do you defend against these attacks? So this is a very very rich area and once again there are many many different techniques. You can have detection techniques combined with some kind of handling. You can have prevention techniques. So one technique for example is to use something like a machine learning algorithm. Something called change point sequential detection which is in the text that I have written. You can use one of those techniques to detect the onset of a DOS attack. And then there are some very standard techniques that are integrated in many modern day operating systems. Those techniques are things like sin cookies and sin cache. So as you might be aware the TCP protocol when you get an incoming request the establishment of a TCP connection is through something called a three-way handshake. So when you receive a connection request when the server receives a request from the client what it does is typically reserve some amount of buffer space. Different operating systems might reserve different amounts of buffer space like for example 300 bytes. So now when you've got many of these attack packets what happens is that a lot of buffer space keeps getting reserved for all these attack packets and it might be the case that it runs out of memory bandwidth or communication bandwidth or CPU processing. It can't process the regular authentic requests and it wastes time in processing all these fake phony requests. So the technique is to use something called sin cache which doesn't reserve the entire 300 bytes but only about 30 bytes for just the basic information on the connection request. So what is the IP address of the person trying to make a connection? What is the port number, the source port number, the destination port number, the source IP address, the destination IP address, the sequence numbers, acknowledgement numbers. All of you are familiar with the TCP protocol and how sequence numbers, acknowledgement numbers work. So only keep that minimal information in your sin cache. And then only when you are convinced after the three-way handshake there is a genuine request only then do you reserve the entire 300 bytes. So that is one technique. There are many, many more techniques compared to just the sin cache and the sin cookies. There are solutions at different levels. For example you have something called DRF distributed route filtering. You have something called egress filtering and so on and so forth. So there are solutions at the host level. There are solutions at the network level. There are solutions within the core of the internet, et cetera, et cetera. So what are the typical types of malware including spyware? So when you think of malware there is an increasing number of these different species now. You think of worms and viruses. These are two examples of malware that can replicate. And then you have got things that don't replicate. The best example is a Trojan. So the main purpose in life of a virus or a worm is to replicate. While a Trojan doesn't necessarily, in fact it does not. What is the difference then between a worm and a virus? A virus spreads from one file to another. So it's like a parasite. It attaches itself to a file and then having attached itself to one file on a computer system it spreads from one file to another file within the same computer system. By contrast a worm spreads from one computer to another computer. So a worm absolutely needs the presence of a network. Whether it's the internet, whether it's propagation vector is email, whether it could spread through Bluetooth, MMS, there's a whole bunch of different types of mobile viruses and mobile malware, et cetera, et cetera. So this is the main difference between worms and viruses on the one hand and Trojans and then between worms and viruses. And then spyware are things that actually can be sent communicated through Trojans that are things like key loggers for example, things that botnets could do. Log in all your keystrokes including your password and then communicate them to some remote site on the internet where the attacker has hosted his own website. So these are all extremely dangerous and getting more and more sophisticated by the day. One important question over here, what are the attacks on a web server and what are the typical vulnerabilities on a web server? So it turned out that the most common types of vulnerabilities that we used to talk about were more vulnerabilities in networking protocols. Then gradually over the last three, four years, it has been mostly application vulnerabilities that have caught the public interest. So I would like to refer you to a particular site. Just go on to the net and do a Google search for OWASP. OWASP stands for Open Web Application Security Project. So this particular organization actually lists the top ten vulnerabilities every year and you can see how these things are changing. So the thing I talked about before namely buffer overflow was a big hit and in fact it's a very, very common vulnerability but it was a big hit say 10 years ago, 5 years ago and so on. But now the latest kinds of vulnerabilities are more the ones that target web applications and the most important of these in fact I believe the number one is injection that is command injection, SQL injection. That's the number one type of vulnerability and amongst the top five are cross-site scripting. So cross-site scripting have become very, very advanced. First generation, second generation, we are right now the third generation cross-site scripting kinds of attacks. So this is something that you must talk about in your class because it's just too important. Cross-site scripting, SQL injection and buffer overflow. So what were the attacks on web servers? Basically these kinds of attacks. There are different kinds of cross-site scripting vulnerabilities. There is persistent, there is non-persistent, there are DOM based and so on and so forth. Again SQL injection that is something that we understand, something that's easy to patch by using parameterized queries and what not. Are there any practical implementation techniques for social engineering? So the next question is what is the most common type of social engineering attack? So the answer probably would be phishing attacks. So there have been many solutions. This is one area of research which combines psychology and computer science and mathematics and so on, many, many different disciplines. There have been many emerging defenses for phishing attacks, some of which try to look at all possible websites that you have referenced and see which is a new website. They try to look at what the website has on it. They try to caution you with red flags and yellow flags and so on that this particular website might be a dangerous website. So there are all sorts of techniques that you will see in the literature. If you want to have a little list of some of these papers that have come up in the last two years, I'll be happy to send them to you. One such technique is called anti-fish, for example. One question here is what is the latest research into malware detection techniques? So once again when we talk about malware, I will just briefly split this question into two parts. One is worm detection and the other is virus detection. So one of the common worms that manifested itself in the early 2000s or 2001-2003 are respectively the code red worm and a worm called the slammer worm. Spread very, very fast and infected about the slammer worm in particular which spread through UDP rather than TCP, infected almost half the vulnerable computers in just half an hour. So it spread so fast before the system administrators could do anything about it. So the question that was in the mind of security experts is how do we somehow retard the spread of these different worms? So there were many good papers in the year say 2004-2005-2006 in the area of worm detection. So guess how this thing could work? So basically in the case of these internet, these are called internet scanning worms, worms like code red and slammer. So what you find is a peculiar, particular characteristic of these worms is that they had, if you don't talk about the polymorphic worms, the regular monomorphic worms is that most of their instances have the same payload. So if I can have some kind of an ideas in my organization, in my campus which looks at the payload of various packets that are coming in and tries to find if there are common substrings, not the entire packet was identical but there were large substrings that were identical. If I can identify common substrings in those different packets that are coming, then maybe that's a trick. Maybe I've been able to figure out that this is the onset of a worm epidemic because these worms spread as I said very fast. They spread around the world and you had many, many instances of these worms that were arriving onto your campus for example. So if I can look at all the different packets that are arriving and identify a common substring, then maybe I've been able to detect a new worm that is coming. So this was the basic idea, how exactly that was done, the pattern matching ideas and so on are described in great detail in the papers in one of these chapters. The other thing was virus detection. So besides worm detection under malware detection, the other thing is virus detection. Now can you use the same technique for virus detection? And mind you, we are talking about now polymorphic worms where the payload looks very different because the worms themselves are encrypted, different instances the worms are encrypted. So different people came up with different ideas. But one of the most powerful ideas that came up with a few years ago was don't look at superficial things like just the payload of a packet but just take a packet, look at its executable and try and see what is the behavior of the executable. So if you are trying to identify different so-called mutants of the same virus and this is what modern-day antivirus products do, they don't has yet do them. But I would see the next generation of antivirus products doing this.  So the signature, the virus signature is not the regular bit pattern in a worm payload but now it is the behavior. Let's look at the system calls made by this piece of software, the operating system calls. Let's look at the sequence of system calls. Let's look at dependencies between these system calls. So there is a lot of very recent research in this area in the last two years or so on virus detection and these more sophisticated virus detection techniques. I'm not sure whether these have ended up being commercial products as yet but I would suspect that they would be in commercial products in a couple of years. I'm very happy to see that these questions are extremely relevant and they really inspire people to think. Maybe I should include them in my exam next time. So the question over here is on wireless. In 802.11 standards, have many security techniques been used and what about future implementation? So this is an interesting question. We all use wireless LANs and you must have heard of terrorists and so on using these wireless LANs to get people's passwords and all sorts of things. Even in our own institute, the students come and tell me, sir, I can get your password from the wireless LAN. I can get anybody's password and that's very, very frightening. So let's look at the brief history of this. The first kinds of wireless LANs which used 802.11 had no security at all. So you could easily make much of the messages, most of the messages were actually being transmitted in the clear. Then they went to a standard called WEP, wireless equivalent privacy or something like that, a wide equivalent privacy. And in my book, I have dedicated an entire section to WEP, not because of why it is good, but why it's something that you should look at its drawbacks. I've tried to illustrate and identify its drawbacks and to give you an example of a protocol that should not be used, of ideas that should not be used. So with WEP, you have many, many, many problems. For example, you can fabricate messages using WEP. You can fabricate messages, you can eavesdrop on messages even though they are encrypted and so on and so forth, a whole bunch of problems with WEP. So the wireless community got together and decided to get rid of all these problems and the solution came up in the form of 802.11i. So there are two commercial names for these standards. One is TKIP and one is CCMP. TKIP stands for Temporary Key Integrity Protocol which gets rid of the problems of RC4. Once again, I have an entire section on both TKIP as well as CCMP. So CCMP is the one that uses still RC4. As I told you before, RC4 has some serious problems, but CCMP has got rid of, let me see, is it CCMP, it's TKIP rather. It's TKIP that has got rid of the problems with RC4 by some clever tricks. While the other protocol namely CCMP decided to start afresh. So they decided to use AES. AES as I mentioned before is the secret key cryptography standard, the latest version, the latest which stands for AES, Advanced Encryption Standard. So this is something that came up about 10 years ago and it's about to replace DES, the earlier standard for secret key cryptography. So CCMP uses AES for two things, for encryption as well as for integrity protection in different modes. So it uses the counter mode for encryption and it uses the so-called CBC mode or cipher block chaining mode for computing MAC. They call it a mic which stands for Message Integrity Code. What is intrusion detection? How do you integrate intelligence and intrusion detection? So intrusion detection is a sort of an idea which you use to figure out beforehand when an intrusion is about to take place. You want to be warned when a denial of service attack is happening or is about to happen and how do you do that? So there are very fancy intrusion detection systems these days that are available commercially available IDS's and most of them use things like machine learning and such techniques. So one of the techniques is sequential change point detection. You can use, there are many statistical techniques that are used for example in forecasting and sequential change point detection looks at a time series and tries to identify when the complexion of that thing is changing, when there is some radical departure from the norm. So you have to identify a baseline, you have to learn. It's a learning technique just like an AI or machine learning you have to learn what constitutes normal behavior and what constitutes a departure from normal behavior something anomalous or abnormal. So that's what an IDS does and it borrows very heavily from machine learning and those techniques including data mining. Is HTTPS always safe? Are attacks possible on HTTPS? Most of us know that HTTPS stands for the S over there stands for secure HTTP. This is a protocol that is used, it's basically SSL a protocol used when you are doing e-commerce or when you are booking airline tickets and so on and so forth. The question is, is it always safe? Well there have been attacks on HTTPS things like the man in the middle attack that are caused due to improper digital certificates. So be very careful about this, the digital certificate and how you actually configure your browser to accept digital certificates. The name of the server, the credentials of the server on the other side is extremely important for this purpose. Also another thing is that SSL is not a panacea for web security. It's not that if I have deployed SSL everything is safe. I just mentioned before that the whole bunch of problems that exploit vulnerabilities in web software like scripting vulnerabilities, SQL injection vulnerabilities every day my students keep finding vulnerabilities in some website or the other. Even very good university websites around the world. So one has to take care of not just deploying SSL but also equally important about making sure the web application software is secure enough. It's audited, there are good coding practices used in designing that software etc. So the next question is about StooksNet and Zeus. How do these botnets work? So I haven't actually looked at the entire working of StooksNet. That's an extremely interesting project for students to do. This worm was released just very recently about two, three months ago. So I haven't looked at the entire working of it. There are many, many papers. It's a very complicated worm by the way and there have been many papers that I've seen on it. Many of these papers are extremely intense and detailed.  So basically these worms are standard botnets and they leverage the power of a P2P network. So they actually are able to pretend to be simple P2P messages out there. And the interesting thing about a bot as compared to a worm is that it's got multiple stages of infection. So first you infect a particular workstation with a bot and then that bot has to communicate to the outside world to various servers to get new code, to get fresh code. So the challenge is how does that bot know whom to connect to? How does that bot know when to connect? For example, if I'm a bot controller, the so-called bot master, I might have 10,000 or even a million computers under my control. Each of them infested by a bot that I've created. I'm controlling each of those computers. I can tell those computers that on the 1st of January 2011 launch an attack on this particular website. I can tell them to generate spam and send them to certain addresses and so on and so forth. Every time I might give them different commands. So this bot is actually working. It's mostly, unlike the Code Red worm, which was very, very active, these bots might be passive for most of their life. And then suddenly I instruct them on the 1st of March, perform this attack. They'll be lying low. You don't even know that they are on your machine. But on the 1st of March, low and behold, all of these in a coordinated fashion around the world decide to attack this particular website in a standard DOS attack or maybe a spamming attack and so on and so forth. So this is the way they work. The main idea in a bot is it gets secondary infections, which are all fresh. I can create an infection and put it on a website in the month of February and instruct all the bots under my control to go and fetch that infection. So it's very difficult for law enforcement authorities and there are all sorts of obfuscation techniques for these bots. It's very difficult for law enforcement authorities to go and to be able to disable these things to figure them out completely because there could be many bots in your campus, in your organization. There could be many PCs that are bot infested and you don't know and you probably never will for a long time to come. So bot detection is a big deal. Hello, sir. Sir, how to find a difference between the cell sign certificate and the CA sign certificate? Between a self-signed and or CA sign certificate. The CA's typically are very well-known entities. For example, take India. First and foremost, internationally, you might have heard of very sign and even RSA, security and so on. These are different organizations that issue that create certificates on behalf of users like the Indian Railways, for example. And then within India, you have got the Outfit Reserve Bank of India's Research Centre in Hyderabad, for example. They create certificates. TCS creates certificates and so on and so forth. So typically, when you use these certificates, you always use them in conjunction with the public key of the CA. So those public keys are known to your browser or should be known to your browser so that they can verify certificates that are signed by those CA's on behalf of other users. So those are the real certificates. And then for a variety of purposes, if you're using OpenSSL to say you've got a class project for your students, you're using OpenSSL, you can generate your own certificates. Of course, nobody is going to accept them in general. You can create your own certificates for purposes of running the experiment, for purposes of verifying the certificate and so on. And those would be self-signed certificates, signed by yourself because a certificate has to be signed by a CA. So you can play the role of a CA just for purposes of your experiment and create those kinds of certificates. Those are self-signed certificates. Because OpenSSL, if you're running an experiment, as my students did here last semester, if you're running an experiment with OpenSSL, you need to have certificates. But you can have toy certificates. Those toy certificates need not be signed by a well-known CA, like very signed or the IDBRT and so on. They can just be signed by yourself for purposes of the experiment. Those would be self-signed certificates. Thank you very much for those very interesting and possibly I should say illuminating questions. I actually love to answer questions. I love to hear questions and think about them. And I think these have been very, very thought-provoking questions. I very much appreciate those questions. I hope I've answered them to people's satisfaction. Whether I have or not, you're free to email me. I know this is a very important set of participants out there.  And I'm sure you're doing an excellent job. This is a very, very interesting field, as you know. There is so much that needs to be done in this field. We need to go on to, you know, this probably an entire MTech program that we set on just security. So it's not one course, as I said. I used to have half a course in IIT Bombay. Then it became one course. Now it's two courses. And some students are saying, let's have a third and fourth course and even an entire MTech in security. So it's a very growing field. It's a field to keep up with so much that is happening. But I'm sure you will be able to do it. Don't forget, the students are young.  You can use your students to do all sorts of wonderful experiments, read all sorts of new papers and new ideas. And we can bring this field of security, we can take this field of security higher and higher in this country. So with that, I end and I wish you all the best of luck.