The hackers are failing to take an early new year break with staff being warned of a new wave of malware attacks.
Web security firm Sophos is warning of new versions of the damaging Dorf worm (W32/Dorf-AE, also known as "Storm") being spread.
New year e-cards are currently a popular way of spreading this worm and others, which are designed to crash corporate networks.
The latest malicious email campaigns contain damaging attachments and links to websites containing malware, and have used a wide variety of seasonal subject lines, including:
A brand New Year 2008
Blasting New Year 2008
Dance to the New 2008 Year tune
Happy New Year 2008 to the one I love
New Year 2008 Wishes
The New Year has arrived
"Many people will be returning to their desks after a lengthy break for Christmas and New Year to a brimming bundle of unread e-mails. The danger is that the holiday hangover will make them less careful about which messages they click on," said Graham Cluley, senior technology consultant at Sophos.