1 in 5 Macs infected with (Windows) malware, study finds

On the heels of recent reports about an uptick of malware for Apple Macintosh computers, a new study from security company Sophos has found that one in every five Macs is infected with malware.

The hitch, though, is that it’s Windows malware that will only kick in if you’re running a Windows OS on the Mac.

Sophos’ study is based on a “100,000 strong snapshot” of Macs that have downloaded the company’s free Mac anti-virus software, the company said.


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The survey did find that one in every 36 Macs (2.7 percent) was infected with malware written for Mac OS X. And Sophos warned that, although Windows malware on Macs not running Windows won’t cause harm to those machines, they could spread the malware elsewhere.

Hackers and virus-writers see Mac users as a “soft target,” Sophos said, because they’re less likely to be running anti-virus and other protective software. Windows has always been the most common target because it’s been by far the most commonly installed OS, and many Mac users have felt immune to such attacks.

Some of the malware infecting the Macs in Sophos’ study dates to 2007, the company said, and could have been found and removed if the users had run a basic anti-virus scan. Sophos recommended that all users take protective steps, such as using its free antivirus software for Macs, which has been downloaded by millions of users.

The most common OS X malware found in the company’s study was OSX.Flashback, which exploits a Java vulnerability and at its peak infected as many as 600,000 Macs worldwide. Those numbers have been dropping since the release of a Java automatic security update that removes the most common variants.

Flashback was found on 75.1 percent of the Macs that had OS X malware, the company said. The second-most common attacks were fake anti-virus attacks, which were found on 17.8 percent of the machines.

For Mac users, Sophos offered these recommendations familiar to users of Windows:

  • Run an anti-virus program and keep it up to date.
  • Keep your security patches up to date, both for the OS and for applications running on your Mac.
  • Be careful about which programs you install, the links you click on and attachments you open.
  • Stay informed about current security threats so you’ll be less likely to fall for cyber criminals’ tricks.

About the Author

Kevin McCaney is editor of Defense Systems. Follow him on Twitter: @KevinMcCaney.

Reader Comments

Wed, Apr 25, 2012 SoutheastUS

EVERYONE should install and run anti-malware software on every machine. Linux users have begun to be targeted, also. NO ONE is immune!!

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