Zorp is a proxy firewall suite and as such its core architecture is built around today’s security demands: it uses application level proxies, it is modular and component based, it uses a script language to describe policy decisions, it makes it possible to monitor encrypted traffic, it let’s you override client actions, it let’s you protect your servers with its built in IDS capabilities… The list is endless. It gives you all the power you need to implement your local security policy.

Features
Using script language as configuration and decision language(Python)
Supported protocols
HTTP/1.1
FTP
SSL
SMTP
POP3
finger
plug
whois
telnet
Able to analyze subprotocols (for example HTTP in SSL)
Can add/remove packet filter rules on-demand
You can write your own proxy modules in Python if a native version is not available
With program stacking it is now possible to make decisions about the traffic based on the results returned by the external program. That way, Zorp GPL can block traffic that an antivirus or spam-filter identifies as virus or spam.

I uploaded zorp-3.9.2.tar to my server. You can find more information at this website. They also have some servers setup for you to test with before you download.