Hello,

I'm trying to restrict access to only http and https on my server at work so my workers can't use other services. I setup squid proxy server and configured to allow only 80 and 443 ports from and to internet, and that's working correctly.
Now i know that there is a way to configure ssh tunneling to bypass my firewall and proxy server. I want to know if there is a way to configure proxy or iptables to recongnize if someone attempts to connect to ssh server at home or some other internet ssh server over 80 or 443 port which are open on my work server and how can i prevent that?

Not directly answering your question, but here are a couple of considerations:

Tried squidguard?

http://www.squidguard.org/about.html

Hopefully you've also considered the possibility that they won't be using ssh directly at all....(ajaxterm anyone?)