OTR

Off-the-record.

Open Source Encryption extension for (over) IM Protocols with plugin for pidgin!

http://www.cypherpunks.ca/otr/

or

aptitude show pidgin-otr

Enjoy the privacy! If you hadn't known yet, at least ICQ is transmitting messages in plain text or the Internet and the local network, so anyone can listen in or probably even inject messages without you knowing it.

OTR seems to solve this problem.