Virus traffic in 2005 halved, according to email monitoring company SoftScan, which found that virus emails accounted for just 1.4 per cent of the total emails monitored.

This reflects a move towards smaller, more targeted viruses which are less likely to be noticed and are more effective at stealing valuable information.

"Phishing will still remain the most visible threat in 2006," predicted Bo Engelbrechtsen, corporate communications manager at SoftScan.

"However, the real risk to organisations' data will come from viruses that have the distinct strategy of trying to stay under the radar of antivirus vendors for as long as possible.

"Early detection of these types of viruses relies heavily on intelligent heuristic scanning that adapts and learns from every message it sees."

Spamming, including phishing, was up 13 per cent on the year and spam currently makes up around 85 per cent of all email.

SoftScan warned that the only way to deal with spam is to educate users, since finding the criminals behind it is becoming increasingly difficult.