Wikipedia’s open contribution system has resulted in the spread of malware after hackers booby-trapped one of its pages.

The hackers changed an article about the Blaster worm on the German version of the online encyclopedia, and added a link that supposedly contained a fix for a bogus new variant of the worm. The “fix” was a piece of code that actually infected PCs, rather than removed malware.

To intensify the attack, the hackers responsible also sent spam to German internet users that recommended they visit the Wikipedia site for more information about the Blaster worm. Because the emails linked back to the Wikipedia site, which is a legitimate site, it was not picked up by phishing filters.

Security analysts warn that this is an example of how hackers are becoming more sophisticated in their attacks and using new methods through social networking sites to distribute malware.