According to Sophos, a new worm which targets only Yahoo Messenger has been spotted in the wild. W32/VB-DZE propagates itself through an old method: it sends infected links to all from your list and it affects the Windows OS as it tries to install itself in the registries. When the worm is installed in your PC it changes the registries so that it is executed when the OS is loaded. Then he spreads itself through the sent links. Sophos recommends not to talk with unknown persons that add you to their lists and not to click on received links through Yahoo Messenger. And, of course, you should keep your antivirus application updated.