The worms feasting upon MSN Messenger are called Kelvir.a, Kelvir.b and Fatso-A, according to MSN and computer security firm Korea Trend Micro on Tuesday. Kelvir.a is being posted in the U.S., Korea, China, Australia, the U.K. and Sweden. Now the mutant Kelvir.b is wreaking havoc.

The worm spreads by sending itself to all the MSN/Windows Messenger contacts on the infected PC, and poses as messages like 'omg this is funny! http://XXXXX.home.att.net/cute.pif.' If users click on the address, their PC becomes instantly infected. Although the worm is labeled "medium-risk," it can lead to other problems like private information leaks.

Another virus, Fatso-A, can spread through MSN Messenger and through peer-to-peer (P2P) file sharing applications. Fatso insinuates itself by using eye-catching phrases like "Annoying crazy frog getting killed.pif", "Crazy frog gets killed by train!.pif", and "Fat Elvis! lol.pif."

Users are advised to make sure a file or URL being sent is safe before downloading it, and to activate vaccine programs before starting the files.

MSN messenger users with version 6.0 or lower should select Tools->Options->Messages ->File Transfer, while version 7.0 users should click Tools->Options-> File Transfer in order to activate the vaccine program.

(englishnews@chosun.com )