New year, new virus. Malware code writers have taken advantage of the change of the year to send out worm-laden emails with the subject “Happy New Year”.

If the attachment is opened, it downloads malware on to the machine and uses it as a tool to sent out more infected emails.

The attachments are titled either postcard.exe or, according to analysts at VeriSign's iDefense Labs; once they've been opened and have riddled a machine with malware, the software looks for open mail proxies to it can send out more spam.

iDefense Labs estimates that the worm is spreading at a rate of about five emails per second on large networks.

The worm is believed to be a new variant of the Warezov Trojan horse and so far is largely undetected by antivirus software.

Pocket-lint and other news websites have been warning since before Christmas about the increase in spam during Christmas and New Year, with hackers taking advantage of the fact that people are more likely to open mail from unknown sources since they're shopping more online.