A web integrity filter ensures the integrity of the content of a web page. If a web server is attacked or becomes inaccessible to users, the Web integrity filter attempts to keep unauthorized information from being released to the public, and only the original content would still go out.
The content filter is a separate device on the network, located between the web server and the router or firewall. The device contains a collection of digital signatures of authorized Web content that is known to be legitimate. When a request is made to the Web server, each object’s digital signature is compared with the digital signature that the device had previously collected. If the digital signatures do not match, the page is considered to be unauthorized and it is immediately replaced with a secure archived copy of the original page, and the software notifies the appropriate personnel via telephone, e-mail or pager.