[PEN-TEST] snoop ona live telnet session?

[Mordechai Ovits <movits () OVITS NET>]

Does anyone know of a tool that will allow me to snoop on a live telnet
session?  I'd like to be able to run this on a firewall to see sessions as
they pass through.  Sort of like what ethereal does with "follow TCP
Stream", but live.
Thanks!
Mordy