A recent study coming from Sophos showed that 1 in 5 Macs have malware on them, leading to headlines proclaiming that 20% of Macs are infected. This misleading claim misses a key point in Sophos’ study, which is that the 20% represented Windows-based malware infections. If anything, Sophos’ results seem to suggest that Macs are the new Typhoid Mary of the Internet.
As the Sophos press release and blog post proclaimed, “1 in every 5 Mac computers harbors malware”, most publications ran headlines with that, and so did a few security experts and vendors wanting to weigh in on the topic. The problem is that the 1 in 5, as mentioned, were carrying Windows-based malware. The actual number of systems reporting Mac OS X-based malware was 1 in 36 (or 2.7%).
“A 100,000 strong snapshot of the millions of Mac computers which have recently downloaded Sophos's free Mac anti-virus software, revealed that 20% of Mac computers were carrying one or more instances of Windows malware. Although Windows malware on Macs won't cause symptoms (unless users also run Windows on their computer), it can still be spread to others,” Sophos’ Graham Cluley wrote on the company blog.
The majority of the OS X infections were from Flashback, which has completely rocked the Mac community and dominated the headlines. So it is no surprise that editors and experts jumped at the 1 in 5 statistic, it’s just that the focus wasn’t where it should be.
“Sadly, cybercriminals view Macs as a soft target, because their owners are less likely to be running anti-virus software. Bad guys may also believe that Mac users are likely to have a higher level of disposable income than the typical Windows user. So, they might believe the potential for return is much higher,” Cluley commented.
We’re not sure where those claims come from, but they make sense. We can’t prove them however, so a grain of salt is needed. Yet, the claim that Macs infected with Windows-based malware pose a risk are legit, depending on the family of malware that they are carrying. Still, not all Windows-based malware will spread from a Mac. Those that do come from shared resources, such as documents or other files.
Research like Sophos’ and the explosive growth of the Flashback botnet, which still infects more than 600,000 systems – even after Apple offered a patch and removal tool– has prompted the call for Mac users to use Anti-Virus.
It’s already been said here on SecurityWeek, but it’s worth repeating. As a Mac user, if you want to use Anti-Virus, do so. Just remember that PCs have been using it for years and they still get infected. Anti-Virus isn’t the silver bullet that some make it out to be.