Doctor Web has revealed that over half a million Apple Mac users have been infected by a Flashback Trojan.
The Russian antivirus firm said that the malware began to spread in February and wasn't closed by Apple until this week. An analyst for Doctor Web tweeted that the number of infected units has reached more than 600,000.
The exploit saves an executable file onto the hard drive of the infected Mac and then goes on to harvest sensitive information including passwords. "The file is used to download malicious payload from a remote server and to launch it." said Doctor Web.
Most of the infected Apple Macs are in the US and Canada at 56.6 percent and 19.8 percent, respectively. The UK comes in third with 12.8 percent, which represents more than 68,000 infections.
The firm recommends that users downloads and install a security update from Apple to prevent their system from being infected.