Mac Viruses are not very common, however, they do happen. If your computer has been running slow or having strange issues, you may want to run a virus scan.
Here is one program:
Here is some information in regards to the Flashback OSX virus:
by Michael Medvedev on 28 February 2012
Lion OS X users don’t need to worry as Flashback.G can infect only the earlier versions of Mac OS X where Java Runtime is out of date (e.g. Snow Leopard). Its danger is that the user wouldn’t know that this malware was installed. Even with the latest version of Java Runtime Flashback.G will ask you to confirm the certificate “approved” by Apple which of course isn’t true.
The main purpose of Flashback.G is theft of user’s personal data and putting them to the cloud, including usernames and passwords for Google, PayPal, eBay and other popular websites. Possible signs of infection may be sudden errors in Safari, Skype and other applications related to the embedded browser content.
So if you saw a window similar to the one shown in this post or experienced bad performance of applications specified above, scan your Mac with MacKeeper’s antivirus right away or use the Geek on Demand service.