Mac users don't typically have to worry about malicious trojans making their way onto their computers. However, according to researchers at Russian anti-virus company Doctor Web, Apple machines are now the target of a fake installer that tacks hidden fees onto mobile phone account bills.

The malicious software is disguised as an installer for a popular application called VKMusic4, which allows users to listen to music via a Russian social media site.

"During the 'installation' process, victims are asked to provide their mobile phone numbers," Doctor Web said in a blog post on its site. "Then, they’re requested to enter a code received via SMS."

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Those who unsuspectingly continue become signed up for a subscription, which charges ongoing fees to their mobile phone account.

"By performing these actions the user agrees to terms of a chargeable subscription and a fee will be debited from their mobile phone account on a regular basis," Doctor Web added. "Such installers usually contain meaningless data or the programs they are supposed to install, which in fact can be downloaded from official sites of their developers free of charge."

Fake installers are nothing new — they have been targeting Windows users for years — but this is the first time they have attacked Mac OS devices.

Images via iStockphoto, bluestocking and Doctor Web