MSN Messenger was the instant messaging client of choice for hackers, thieves and many types of malware in 2007. The IM client received 45 percent of all malware threats -- more than double the amount any other service received...Yahoo received 20 percent, AOL Instant Messenger received 19 percent, and all other IM networks received 15 percent combined.

The lack of security features coupled with the fact that IM programs are almost always running in the background of a computer make them extremely dangerous...