Customers ask us regularly to recommend anti-virus software for their Mac. Many of these are converts from the PC world and are accustomed to needing it. There are several reasons why it’s largely unnecessary.
Since OS X 10.6.8 Apple has included anti-malware that is built into the OS. There was a lighter version in 10.4 and 10.5 called File Quarantine that confirmed with the user that files and applications downloaded from the Internet were intentional and approved. In 10.6.8 File Quarantine was enhanced to include actually checking downloaded files against a list of known malware and malware types/signatures. Again, this is built in.
Apple has also established that many anti-virus programs interfere with Apple updates which is part of their argument for advising against them.
The last two large reasons are the main difference between PCs and Macs and are probably the most important. The Mac OS uses compartmentalization, or ‘sand-boxing.’ This means that applications are limited and isolated to the resources they need to access. This is very different from Windows operating systems where this isolation doesn’t exist and malware can attack system and other resources, although as of Windows 7 this is improving.
Lastly, the argument most commonly given is that Macs have a smaller footprint in the market and are less appealing to hackers who must invest great resources in the development robust malware and viruses. This is diminishing somewhat as Macs become more popular, but it’s still true.
Apple still tows the line that anti-virus software for modern Macs is unnecessary. I was a PC tech for fifteen years and dealt with at least one virus for a customer a week. In the year I’ve been working on Macs, I haven’t seen a single one.
So, rest assured that your Mac is safe and installing anti-virus software has the risk of doing more harm than good.