However, the news is not all bad. Advertisers and websites are getting better about detecting the malicious campaigns. The lifetime of an advertising attack continues to fall, with malvertisements removed in an average of 9.8 days in the fourth quarter compared to 11.2 days in the third quarter and 11.8 days in second quarter of 2010.
Part of the problem in detecting malicious advertisements is that every visit to a company's website may not trigger the attack. Malvertisements typically come from a pool of possible ads, which means a company will not be able to verify a customer's complaint that the website is serving up attacks.
"Often a user will simply reload the Web page, a different ad will be shown, and it will be too late to capture forensic information," Dasient states in the report.
This story, "Third-party content is the Web's third rail," was originally published at InfoWorld.com. Get the first word on what the important tech news really means with the InfoWorld Tech Watch blog. For the latest developments in business technology news, follow InfoWorld.com on Twitter.