Dancho Danchev reports in the Zero Day blog on ZDNet that dangerous malware is included with some free Mac screensavers available at 7art-screensavers.com. Intego researchers have identified the malware as the OSX/OpinionSpy spyware.

In a nutshell, “it injects code, without user intervention, into Safari, Firefox and iChat, and copies personal data from these applications.”  It then regularly sends the information, such as e-mail addresses, iChat message headers, and URLs to a number of servers.

You can get the full details both in the ZDNet blog above or from the Mac Security blog.