What is the best way to content-filter incoming HTTP pages (responses), before displayed by browser? One solution is a (transparent) proxy. Is there a better solution (less intrusive, easier to develop, install and maintain)? In particular, can this be done as FireFox extension?
Our motivation: malicious content attack are often via web pages loaded into the browser. For example, a page may include malicious script, either from a rogue site or due to reflection XSS attack. We work on a mechanism to block such attacks; this will be a kind of
browser firewall, with advanced protection capabilities against malware (including XSS), phishing and spoofed web sites. This is part of our plans for next generation of TrustBar, a FireFox extension we made, that allows users to identify trusted web pages, either by a name/logo assigned by the user (petname/petlogo), or by displaying details of the site owner as identified in the SSL/TLS public key certificate, e.g. PayPal Identified by VeriSign. BTW, the last feature was apparently adopted into IEv7.
Notice: many FireFox extensions block objects based on their URL (e.g. AdBlock, NoScript). But we want/need content filtering...