Web Application Security

When you hear talk about Web application security, there is a tendency to immediately think about attackers defacing Web sites, stealing credit card numbers, and bombarding Web sites with denial of service attacks. You might also think about viruses, Trojan horses, and worms. These are the types of problems that receive the most press because they represent some of the most significant threats faced by today’s Web applications.

These are only some of the problems. Other significant problems are frequently overlooked. Internal threats posed by rogue administrators, disgruntled employees, and the casual user who mistakenly stumbles across sensitive data pose significant risk. The biggest problem of all may be ignorance.

The solution to Web application security is more than technology. It is an ongoing process involving people and practices.

Security is fundamentally about protecting assets. Assets may be tangible items, such as a Web page or your customer database ? or they may be less tangible, such as your company’s reputation.

Security is a path, not a destination. As you analyze your infrastructure and applications, you identify potential threats and understand that each threat presents a degree of risk. Security is about risk management and implementing effective countermeasures.

The Foundations of Security

Security relies on the following elements:


Authentication addresses the question: who are you? It is the process of uniquely identifying the clients of your applications and services. These might be end users, other services, processes, or computers. In security parlance, authenticated clients are referred to as principals.


Authorization addresses the question: what can you do? It is the process that governs the resources and operations that the authenticated client is permitted to access. Resources include files, databases, tables, rows, and so on, together with system-level resources such as registry keys and configuration data. Operations include performing transactions such as purchasing a product, transferring money from one account to another, or increasing a customer’s credit rating.


Effective auditing and logging is the key to non-repudiation. Non-repudiation guarantees that a user cannot deny performing an operation or initiating a transaction. For example, in an e-commerce system, non-repudiation mechanisms are required to make sure that a consumer cannot deny ordering 100 copies of a particular book.


Confidentiality, also referred to as privacy, is the process of making sure that data remains private and confidential, and that it cannot be viewed by unauthorized users or eavesdroppers who monitor the flow of traffic across a network. Encryption is frequently used to enforce confidentiality. Access control lists (ACLs) are another means of enforcing confidentiality.


Integrity is the guarantee that data is protected from accidental or deliberate (malicious) modification. Like privacy, integrity is a key concern, particularly for data passed across networks. Integrity for data in transit is typically provided by using hashing techniques and message authentication codes.


From a security perspective, availability means that systems remain available for legitimate users. The goal for many attackers with denial of service attacks is to crash an application or to make sure that it is sufficiently overwhelmed so that other users cannot access the application.