"What about Macs and Linux? There’s a common
notion that Mac OS is an inherently more secure operating system
than Windows, and thus, less susceptible to malware. It’s
true that malware is less prevalent on Macs, but what makes it so
is the relatively small market share (about 5% according to the
latest data from Net Applications). This translates into far less
incentive for malware creators to find and exploit security holes,
and limited potential for nasty stuff to propagate if they do.
"That said, Mac-based malware does exist, as do tools that
provide protection from it. ClamXav is free and open-source
antivirus software for OS X 10.3 and above, PC Tools’
iAntivirus is a free/pay offering, and many of the aforementioned
commercial Windows anti-virus vendors offer Mac versions too.
"As for Linux, the same general rule applies—safer than
Windows, but not categorically safe. AVG offers a free Linux
version and ClamAV is available for, and sometimes included with,
many Linux distros."