Since the malware Flashback re-surfaced, Macs are under attack day and night. According to the security team at Oxford University, the Flashback malware episode is the worst since the Blaster worm of 2003. Flashback exploits a vulnerability in Java which allows 'drive-by' downloads! The team continues to say that Macs are being attacked on a very significant scale, and Apple is 'making minimal effort' and 'putting customers at risk'. Mac malware has gone mainstream.
Read the full blog post here - http://blogs.oucs.ox.ac.uk/oxcert/2012/04/25/musings-on-mac-malware/