Stephan Chenette, manager of Websense Security Labs, said that while security vendors differ on many things, they pretty much all agree that compromised legitimate sites currently serve most of the malicious code in circulation.
And it's not just small sites being subverted to serve malware. "Sixty percent of top 100 sites are either involved in or had malicious content in last 180 days," said Chenette.
Twenty-nine percent of malicious Web attacks include code that steals data, the Websense report says. Of those attacks, 46% steal data over the Web.
Ninety of the top 100 sites are either social networking or search sites, according to Websense. More than 45% of them support user-generated content.
The problem, said Chenette, is that so many Web sites allow users to upload content, but they don't filter it carefully. He cited Google Page Creator Web pages and Blogger Web pages as "hosting a tremendous amount of malware."
"As more organizations and their employees are adopting Web 2.0 technologies for legitimate business reasons, users are given privileges such as directly editing Web content or uploading files -- potentially causing more security issues as many organizations lack the adequate security technologies and practices to enable safe Web 2.0 use," the report says. "The increase in Web 2.0 applications has allowed hackers to target users and businesses using mash-ups, unattended code injection, and other tactics providing yet another level of complexity for organizations and users that want to prevent data loss and malicious attacks."
Compounding the problem is the tendency of many Web 2.0 sites to focus more on size than on security. The Web 2.0 business model looks a lot like that pursued by the credit card industry, where high rates of fraud and payment defaults are tolerated to maximize the possible base of interest paying customers.
"If [Web sites] have more users, they are willing to take some of those security risks," said Chenette. "They find that the value of having more users is more valuable than [the risk of] having certain security flaws."
A further complication is that Web URLs are no longer a meaningful indication of the source of Web page content. Web pages now may include multiple iframes, which call out to servers that may not be apparent to the user to fetch content or code.
There is some good news, sort of. Twelve percent of Web sites with malicious code were infected using Web malware exploitation kits. That represents a 33% decrease since December 2007. Websense attributes the decline to a shift toward customized attacks as a way to avoid detection.