According to a Department of Trade and Industry (DTI) report into information security breaches, viruses remain the biggest cyberthreat to businesses. The survey found that virus infections were also more likely to have caused serious service interruption than other incidents. Launched at Infosecurity Europe 2006 in London in April, the study also highlighted the growing threat of spyware and phishing.

"Usually the disruption was minor, but roughly a quarter of companies questioned who reported a virus as their worst incident had major disruption, with important services such as email down for more than a day," the authors of the survey said in a statement.

"Of external threats, malicious software was the most significant, while the threat from spyware grew the most. Spyware was the hardest threat to detect, and the one UK businesses were least prepared for," Chris Potter, co-author of the report and partner at PricewaterhouseCoopers, told ZDNet UK.