Content-based packet filtering proxy

Question

I want to set up a proxy server, which upon getting specific pattern in HTTP response body (a 403 Forbidden, with some special content), reroutes the packet some other way (through another proxy, for example). Which proxy servers may be used? And how?

Answer 1

ModSecurity can do this, have a look at this:

http://www.modsecurity.org/documentation/modsecurity-apache/1.9.3/html-multipage/05-actions.html