How to block my users to execute telnet commands?

[pingping]

I have some network users who used telnet to chat other
users outside my network. How can I stop them to used
telnet? What is the best way to block those users? Thanks

 

[Steven L Umbach]

There are a couple of ways. Receving computers could have the telnet service
disabled. Client computers could have deny permissions applied to the telnet
executable - where ever they may be on the computer. The best way in my
opinion would be to block access to outgoing port 23 at the firewall/router
or use ipsec filtering on client computers to accomplish the same which
could be enabled via group policy. --- Steve

http://www.securityfocus.com/infocus/1559 How to use ipsec filtering.