Web Content Filtering with ISA Server

Response-String Filtering
Through URL filtering, you can gain a large amount of control over the security of your network. You can even block off entire country top-level domains (e.g., *.cn for China) from your user community. However, in some cases, content filtering based on URL checking isn't enough. You can't know in advance all possible unacceptable URLs. Also, some Web sites with questionable content don't operate on URLs but solely on IP addresses. For those situations, ISA Server provides an additional content-filtering tool in the form of response-string filtering.

Let's look at how response-string filtering works. You might want to ban all Web sites that refer to United States Code 18, section 2257, a common disclaimer-that adult content sites use on their logon page to confirm that they operate within the law. Typically, the notation appears as 18 U.S.C. 2257. If that notation appears on a Web page, the odds are pretty good that the page is part of an adult Web site. . . .