Flashback appears to be the most widespread Mac malware we’ve seen since the days when viruses were spread on infected floppy disks; it could be the single most significant malware infection to ever hit the Mac community.

Rich Mogull provides the definitive explanation of Flashback. If you want a sensible, non-sensationalist view on this threat written by a security expert, EMT and a former [something I swore to Rich I’d never tell anyone about], read this piece.