As for the new samples that appeared this week, PandaLabs report about the MsnChristmas.A worm, and the Yahmail.A and Banbra.FEM Trojans.
The MsnChristmas.A worm spreads to Messenger contacts in messages like "Christmas photo! :D", "vengo de fi este foto" or "Hey i que hace el"
which contain an infected attachment called "img2007-12.JPEG.scr". If the recipient of the message runs the file, the worm will install on the system.
Yahmail.A is a Trojan that can either be dropped on the system by other malware or sent in a spam message. This malicious code is designed to steal user names and passwords for the Yahoo! instant messaging application and send them to a certain Internet address.
Once installed on the target computer, Yahmail.A creates several copies of itself on the system and inserts a series of entries in the Windows registry. This way, it ensures it is run every time the system is started up.
Finally, Banbra.FEM is a banker Trojan, designed to steal login data for certain online banking services and Internet payment platforms.
To check if your PC is infected, you can use NanoScan.