It’s estimated that 600,000 Macs are infected with the Flashback botnet, evidence that OS X is becoming a more popular target for attackers. Be sure to apply the OS X Java update that came out recently, and use a virus scanner for a little extra protection.
http://news.cnet.com/8301-1009_3-57409619-83/more-than-600000-macs-infected-with-flashback-botnet/