Researchers at the security firm M86 report that hackers have compromised hundreds of Web sites that use the Wordpress content management system. The sites, mostly small Web pages and blogs, are being used to fool spam filters and redirect unwitting visitors to drive by download Websites that will install malicious software on vulnerable systems.

Amid an increase in defacements of legitimate websites over the past few weeks, Fraser Howard, a researcher from Sophos, has discovered that the groups behind the attacks are increasingly using sophisticated filtering and dynamic content to avoid detection by search engines and web filtering firms.

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