~~~~~~~~~~~~~~I just posted an FYI set of notes over at MacDaily news to help sort out some misinformation regarding what has been occurring thanks to the Russian malware rats who write the Flashback series of malware. It may be helpful here as well.
The worst previous Mac malware infection was due to Trojan.OSX.iServices.A-C. It was a Trojan horse that was infiltrated into Warez versions of a few different Mac apps available at Torrent websites. The result was a botnet estimated to contain 10,000 Macs. That was in early 2009.