Secure Instant Messenging
Trillian offers a way to do SecureIM in AOL, but not other IM clients. I think this is a plugin for MSN Messenger, not trillian or other clients that connect to MSN.
SimpLite, the free instant messengers security
You are using instant messaging software to chat with your friends or colleagues. Did you know your messages are sent over the Internet in cleartext form?
By encrypting messages before they leave your computer to the Internet, SimpLite-MSN prevents eavesdroppers from reading your personal MSN Messenger conversations. As the original successor of Simp 1.0, SimpLite-MSN benefits from state of the art algorithms to secure your messages, whilst maintaining an intuitive interface.
SimpLite-MSN is free for a personal use at home or at the office. The only restriction is that only one product from the SimpLite family can be launched at the same time: either SimpLite-MSN, SimpLite-AIM, SimpLite-ICQ or SimpLite-Yahoo!.
We also recommend that you check our new SimpPro, especially designed for corporate environments or more demanding home users.