63.4% of businesses said they agreed with the statement: "Maintaining internet security is extremely challenging for my organisation". Just 4.5% of respondents said they strongly disagreed.
The poll was conducted among board level executives and IT professionals in 313 UK businesses. It found great concern over malware, which led to a loss of sales in three out of ten businesses surveyed. Other results of failing to stop malware were compromised information and a decline in worker and IT department productivity.
The survey also found widespread concerns over the explosion of social networking sites. Nine in ten businesses said sites like Facebook and MySpace were causing an online security threat, which one in five companies described as "major". But firms remain reluctant to block access to these sites, with just 34.8% of companies imposing a restriction.
In terms of types of attacks, the most dangerous are malicious spyware, those taking advantage of browser vulnerabilities and web application exploits, according to the respondents.
Just 84% of firms said they were using desktop security software to protect their organisation, with the others reliant on gateway products and hosted security.
"Things are becoming more challenging for IT admins. Unique samples of malware are up 500% year-on-year," said Michael Irwin, Webroot Software's chief operating officer. "The flipside is IT managers are trying to get more efficient, but budgets aren't necessarily increasing."