To combat these new threats one needs to look at different strategies as well. In this paper we shall look at different approaches and tools to improve security posture at both, the server as well as browser ends. Listed below are the key learning objectives:
• The need for Ajax fingerprinting and content filtering.
• The concept of Ajax fingerprinting and its implementation in the browser using XHR.
• Processing Ajax fingerprints on the Web server.
• Implementation using ModSecurity for Apache
• Strengthening browser security using HTTP response content filtering of untrusted information directed at the browser in the form of RSS feeds or blogs.
• Web application firewall (WAF) for content filtering and defense against Cross-Site Scripting (XSS)

Requirement for Ajax fingerprints and filtering
Ajax is being used very liberally in next generation Web applications, forming an invisible layer in the browser’s transport stack and bringing to the fore numerous browser-related attacks, all centered around Ajax. Although Ajax applications hold a lot of promise, there are loopholes being exploited by viruses, worms and malicious attackers in Web 2.0 applications that need to be looked at a little more closely. Ajax hides a lot of server-side critical resources due to its calling mechanism, bringing in sloppiness in coding patterns and fueling vulnerabilities in the server-side application layer as well. Untrusted resource processing from blogs, feeds and mash-ups are making Ajax vulnerabilities relatively easy to exploit. In such situations Ajax request and response fingerprinting and filtering mechanisms can enhance the security posture of Web applications. Web 2.0 applications have a special set of resources that are accessed by the web browsers over Ajax calls using the XMLHttpRequest (XHR) object. Resources can be grouped into two broad spaces – one with “Ajax-only” access and other non-Ajax (traditional) resources. In the application architecture, one can wrap security around Ajax resources by creating a separate virtual sandbox for all incoming and outgoing Ajax calls.

Download pdf ModSecurity Use Case: Web 2.0 Defense with Ajax Fingerprinting and Filtering