The firm's biannual State of Internet Security (PDF) report is compiled using email and web site scanning data collected by Websense Security Labs. The report found growth not only in the number of malicious sites but in the continued activity designed to compromise legitimate sites.
In the first half of 2009, over three-quarters of web sites with malicious code were found to be legitimate sites that had been compromised. Recent widespread attacks such as NineBall and Gumblar were blamed for injecting malware into sites on a huge scale.
"People can do a lot to protect their sites from being exploited, including examining their code, looking for vulnerabilities in their servers, and keeping any third-party applications patched," said Websense EMEA threat manager Carl Leonard.
Leonard also urged end users to employ real-time web scanning technology which will prevent them from visiting malicious sites even if they have been recently infected.
Websense also warned firms that encourage user-generated content on their sites. The report found that 95 per cent of user-generated comments on blogs, chat rooms and message boards are spam or malicious in intent.
"The attack surface area is increasing, and malware authors are targeting where users will be in their tens of thousands," said Leonard.
"If you have a site with a blog feature or somewhere users can post comments, it's very likely that malware authors will also want to use the feature to push out malicious links. They need to be filtered in real time."