Russian anti-virus firm Dr Web has warned that nearly 600,000 Mac computers have installed Flashback Trojan – a malware that is capable of jeopardising user security online.

More than half of the infected Macs are from the US, Dr Web report says, informing that users can counteract the virus by installing a newly-released security update patch from Apple.

First spotted in September last year, Flashback Trojan is known to exploit loopholes in Java to auto-install a code without user’s knowledge. The virus is capable of penetrating some of Mac’s security walls, the Russian firm says.

The virus was first used by security analysts as a Flash Player update and following the installation it shot a message to the hacker’s system with a code unique to the targeted system.

This code can give a potentially all-powerful toolkit to the intruder, Dr Web’s chief executive Boris Sharov warned, saying that it can transfer control of the machine to unknown hands, exposing it risks of security breach.

The UK is amongst the countries where the bots are found active, according to the anti-virus firm. The other IP addresses that have been identified as threatening are from the US, Canada and Australia.

Oracle’s fix to the issue in February proved unfruitful for Mac as Apple regulates Java updates for its computers. Quite clearly, the virus threat shows that Apple is not invincible, as many users like to believe, a security analyst at anti-virus firm Kaspersky said.