IT systems were hit with 50% more viruses in 2004 than the year before, and the damage done continues to grow, according to a survey of 300 companies and government agencies.

Respondents to the Virus Prevalence Survey reported 392 incidents per 1,000 machines, and when 25 or more PCs or servers were infected, system downtime increased by 12% in 2004 compared with a year earlier, according to the poll, which was sponsored by McAfee, Microsoft, Trend Micro, and other vendors and conducted by ICSA Labs, a division of Cybertrust Inc.

The time it took to recover from the infections last year increased by seven person days, year over year, and the cost of recovery averaged $130,000. Both of those figures are 25% higher than in 2003. Ninety-one percent of those surveyed say the threat from malicious code is getting worse; no one says it's lessening.

Many companies have deployed antivirus software, but the number isn't as high as it should be, says George Japak, VP of ICSA Labs. "The controls exist to mitigate problems from viruses," he says. "A lot of companies still don't have those, and that's why the infections rate is still so high."