Integrity checking can be
Integrity checking can be used to identify a type of these things that operate at Ring 0. Some of these things use a polymorphic engine to obscure their signature. A recent example of these things called Cryptolocker encrypted file contents. They're often used to create large numbers of zombies and particularly hard to detect examples of these entities are called (*) rootkits. Melissa was one of many of these things that took advantage of macros, but more modern examples of them often use zero-day exploits reported to the Common Vulnerabilities and Exposures index. These programs are studied by Kapersky Lab and one of them called Stuxnet was used against the Iranian nuclear program. For 10 points, name these types of malware.