Beyond of this, tor also open a tunnel on the firewall. Suppose you livein irc.freenode.net but the port 6667 is blocked by the firewall. You can torify irssi to using the hidden service, and keep you IP private, – one stone kills two birds!
Add this line to /etc/tor/torrc
mapaddress 10.40.40.40 mejokbp2brhw4omd.onion
Run irssi in torified mode:
$ torify irssi
conn 10.40.40.40 to access irc.freenode.net
If you don’t have the privilege to access /etc/tor/torrc, you need socat to relay the tor network to your local socket proxy:
$ socat TCP4-LISTEN:6667,fork SOCKS4A:localhost:6ua4nhltph56henu.onion:6667,socksport=9050
Then you can run irssi and
There is a more detailed HOWTO about the onion router.