information taken primarily from a blog post that shows an MSN bot in action as well as detailing how it works and why they exist

An image is sometimes worth a thousand words.  The picture below we grabbed from a blog by Dancho Danchev , and shows infected bots spreading spam messages at MSN via IRC based command and control.  There's also a diagram at the blog that illustrates at a high level how this works.

Several researchers have theories about why the number of IM attacks is increasing.  Don Montgomery, Vice President of Marketing at Akonix, speculated the increase in the number of attacks reflects the increase in the use of instant messaging - particularly on corporate networks.   "IM is becoming favoured over e-mail as a distribution vector for malware as a result of e-mail security now being employed by 75 percent or more of companies, while IM security is only employed by 15 to 20 percent of companies," Montgomery said.  "The hackers are simply turning to the open door".

The blog post goes on to suggest that "either someone's spamming p3n1$ enlargement propositions and directing to a spam site, or the social engineering efforts aim at getting the IM reader to visit an exploit hosting site."  It continues, "no more direct .pif; .scr;; or .exe propositions in plain simple text, what's exploited is mostly client-side vulnerabilities and redirectors to break the ice."