Almost half of UK businesses suffered a virus infection or a denial-of-service attack last year, research shows.

The figures from the Department of Trade and Industry's biannual Information Security Breaches Survey conducted by PricewaterhouseCoopers, shows that attacks affected 49 per cent of companies last year, up from 41 per cent in 2002, and 16 per cent in 2000.

The disruption to companies whose systems were affected ranged from minimal disruption to a major problem, impacting systems for a month or more.

The findings, which will be published in full at this year's InfoSecurity show, coincide with the spreading of a new mass mailing worm, Netsky-D, which was given a four out of five severity grading by anti-virus vendor Symantec.

John Meakin, group head of information security at Standard Chartered Bank is not surprised by the findings.

'For us as a company, in line with other large corporates, we have been affected in a big way,' Meakin said. 'By far the most significant effect is the man-time used reacting to virus and cleaning up afterwards.'

Meakin says companies are getting better at dealing with attacks, something that will become essential as virus attacks become more malicious.