Web Application Firewall

Applications that provide services to end-users can be vulnerable to many threats. Although many of these threats can be prevented by application developers, this often is outside the web site owner's control. A web application firewall (WAF) provides a layer of control between end-users and applications.

A WAF filters all application access, inspecting both the traffic towards the web application and the response traffic from the application. By securing both the application infrastructure as well as the application user, a WAF complements traditional network firewalls, which are not designed to protect at this granular level.

Threat Vectors

Applications can be vulnerable to many threats that are not detected by regular network firewalls. The impact of these attacks can be quite severe. The Open Web Application Security Project (OWASP) has compiled a list of the top 10 risks that still threaten many web application deployments. The top 10 of 2010 is virtually identical to the new 2013 version; the most common attacks have not changed dramatically over the years. Here are some examples:

· Injection: SQL Injection Attacks use a Web form or other mechanism to send SQL commands or commands containing SQL special characters. By sending these SQL commands, the attacker can trigger the backend SQL database to execute the injected commands and allow unauthorized users to obtain sensitive information from the database.

· Cross-site scripting (XSS): XSS attacks exploit a Web server that does not validate data coming from another site. XSS can enable the attacker to obtain sensitive information, or to compromise a Web server.

· Sensitive data exposure: If Web applications do not protect sensitive data such as credit card numbers or Social Security Numbers (SSN), attackers are able to conduct identity theft, credit card fraud, or other crimes.

· Cross-site request forgery (CSRF): CSRF attacks force a user to send an HTTP request, including the victim's session cookie, to a vulnerable web application. To the vulnerable web application, this appears to be a legitimate request coming from the victim.

Attack Mitigation Examples

The WAF module offers granular control of Web application data flows. The WAF has various ways of dealing with threat vectors that can be launched at web applications. Here are two use cases:

· The WAF can prevent buffer overflow attacks by setting accepted maximum thresholds for aspects of HTTP requests, and blocking requests that exceed the configured limits.

· The WAF can strip HTTP response headers to “cloak” server information that can equip a hacker to target an attack on your Web servers. For example, the WAF can cloak an HTTP response header to hide the operating system that is running.