Apple on Thursday released an identification and removal tool for the most widespread virus ever to hit its computers.

The Java security update removes the most common variants of the Flashback malware, which was found to have infected some 600,000 Macs last week.

The malware, discovered last week by Russian security firm Dr Web, is designed to grab passwords and other information by posing as a legitimate browser plug-in at a malicious website. Once installed, the software sends personal information back to remote servers.

The Mac operating system was previously widely thought to be immune to the widespread security issues that have plagued Windows computers over the years.

Apple’s patch was rushed to users several days after independent security companies issued their own patches for the malware.