Malwarebytes takes a look at a method cyber-criminals have begun using to target Mac users with "ransomware", hijacking the user's browser with a notice demanding payment of $300 in order to release control of the application. While similar malware has affected Windows systems for a number of years, Mac users have only rarely seen such efforts targeted at themselves.

The ransomware page is being pushed onto unsuspecting users browsing regular sites but in particular when searching for popular keywords. Warnings appearing to be from the FBI tell the victim: “you have been viewing or distributing prohibited Pornographic content.. To unlock your computer and to avoid other legal consequences, you are obligated to pay a release fee of $300.”



Rather than a sophisticated hijack of the actual browser software or an installation of a trojan, the ransomware is merely a simple webpage using JavaScript to load 150 iframes that require confirmation to be dismissed, with the authors hoping that users will give up long before they dismiss all of the dialog boxes and simply pay the ransom. As the report notes, a feature on OS X that reopens previously open windows after relaunching an app means that users generally can not simply close and reopen Safari in order to escape the ransomware.

The report details one method to escape the ransomware involving resetting Safari, but misses a far simpler tactic: Simply holding down the Shift key while relaunching Safari will prevent it from reopening windows and tabs from the previous session. Users can also completely disable the reopening feature across OS X from the General pane of System Preferences. Many OS X users may, however, be unfamiliar with such options and find themselves trapped by the ransomware webpage.

The report notes that the ransomware authors are targeting users based on popular search terms, with one example stumbled upon through an image search result for Taylor Swift on Bing.