It was long thought that Macs were impervious to malware, viruses, slowdowns, and other typical "PC" problems. However, due to the increasing popularity of of the Mac operating system, hackers have turned their sights to the once immune platform.
"Attackers dearly care more about Macs now But we need to keep our perspective: There's still far less malware aimed at Macs than at, say, Android phones. Nevertheless, Flashback is a significant development. We'll see more malware on Macs, but as long as we all take precautions and stay vigilant, the attacks will be infrequent events rather than the continuous onslaught of epidemics that some observers are predicting. " ~Mogull, Rich. "The Flashback Trojan horse explained: we've entered a new era in Mac security, but there's no need to panic." Macworld July 2012
Macs are based on the Unix operating system, which is much harder to hack. However, it doesn't mean they are immune. The recent "shellshock" bug proved that - a vulnerability that would potentially allow a hacker to gain control of the victim's computer. These things and more are reason enough to put a little bit of protection on your Mac. There have also been numerous cross-platform malware attacks lately, ushering in a new era of Mac security. It's all about prevention, though, so following proper protocol to prevent viruses is key for all computers.
Another thing that Macs are no longer immune to is file clutter and other problems. Recently there have been some software programs that have been created to help Mac users better manage their computers.
Mackeeper is one such program, and you can easily and quickly install it to help optimize your system. There has been a bit of controversy over Mackeeper but it's a safe program. The thing is, you don't need it if you don't need it. If you're having problems with your Mac, however, it might be a great alternative to that annoying appointment at the Genius Bar.
So what can you do to keep yourself safe? Follow the standard operating procedure of all computers. Don't download unknown attachments, only download and install software from VERY trusted sources (a random downloads website is not a trusted source), don't browse in internet bad neighborhoods, and back up your important data on the regular. Don't download lots of torrents or other file sharing types.
And that's about it. It's really not that hard, but sometimes viruses slip through, and in the case of the shellshock vulnerability it doesn't even seem that you have to have downloaded something weird to get attacked.