Did anyone find a solution to forbid Instant Messaging (yahoo, msn, aol, ....) by applying a specific rulebase on the cisco/checkpoint firewall? The problem is these Instant Messaging software use HTTP protocols to sneak thru firewalls. Maybe something could be done on the proxy server?
Thanks.
Get cybersitter and use that. I used that before it started clashing with programs on my network server, and it blocked these services quite well. Cybersitter will work on a network server, and filter all the machines behind it. If you need to block instant messaging, CyberSitter is your best solution, provided it does not clash with any programs running on your network server. Some programs running servers on your machine may clash with CyberSitter, but if that will not be a problem, then I recommend CyberSitter, and blocking the categories of Free Email and Online Chat, that will stop the three major messenger services (MSN, AIM, Yahoo)
Thanks for this answer. I'll try it out.
Sonicwall and Netscreen firewalls will do this (I think the Sonicwall supports more options).
Some people block the IP addresses this programs as primary servers, the ones they connect to login. Others use some strings extracted from the login sessions of this programs to block them. You can find more information on Internet, there are some sites that have information about this subject. You can also use a sniffer as ethereal to create your own rules.
I did my little searches on my side and I found that Snort had a "chat.rules" which could spot most of the Intant Messaging solutions.
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