Damage to business IT systems caused by viruses continues to grow, and businesses are getting hit by more viruses, according to a new survey. IT systems were hit with 50% more viruses in 2004 than they were in 2003, reaching 392 incidents per 1,000 machines, according to a survey of 300 companies and government agencies sponsored by McAfee, Microsoft, Trend Micro, and other vendors, and conducted by ICSA Labs, a division of Cybertrust Inc.

The Virus Prevalence Survey indicates that when 25 or more PCs or servers are infected, system downtime increased by 12% in 2004 compared with a year earlier. The amount of time it took in 2004 to recover from the infections increased by seven person days, year over year, and the actual costs of recovery averaged $130,000. Both of those figures were 25% higher than in 2003.

The majority -- 91% -- of those surveyed said the threat from malicious code was getting worse; no one said the threat was lessening.

While many businesses have deployed anti-virus software, 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 infectious rate is still so high."