"Worm-laden messages are titled "Happy New Year" and contain an attachment called either postcard.exe or postcard.zip, according to experts at VeriSign's iDefense Labs, which provides information on security flaws and exploits. If the attachment is opened, malicious software is downloaded from the Internet and can infect computers running Windows operating systems."
For social reasons we tend to be more likely to open these kinds of emails during the holiday season. Because we expect them, we may not be as careful as we normally would be. So keep your guard up and don't open "Happy New Year" emails willy-nilly. And anyway, if someone wants to send you a proper greeting they should send you a card or make a stinking phone call, right? Right.