SAN FRANCISCO - Computer security firm Sophos on Monday warned that scammers are duping Facebook users with a bogus "Dislike" button that slips malicious software onto machines.

There is no "Dislike" version of the "Like" icon that members of the world's top social networking website use to endorse online comments, stories, pictures or other content shared with friends.

Hackers are enticing Facebook users to install an application pitched as a "Dislike" button that jokingly notifies contacts at the social networking service "now I can dislike all of your dumb posts."

Once granted permission to access a Facebook user's profile, the application pumps out spam from the account and spreads itself by inviting the person's friends to get the button, according to Sophos.

The ruse was described as the latest in an ongoing stream of tricks that includes baiting booby-trapped links with messages including "the biggest and scariest snake" and "world's worst McDonald's customer."