Adobe is aware of malware posing as its Flash Player and warns users to ignore any updates that didn't originate on its own servers. "Do not download Flash Player from a site other than adobe.com," said David Lenoe, Adobe's product security program manager, in an entry on Adobe Product Security Incident Response Team's PSIRT blog. "This goes for any piece of software (Reader, Windows Media Player, QuickTime, etc). If you get a notice to update, it's not a bad idea to go directly to the site of the software vendor and download the update directly from the source. If the download is from an unfamiliar URL or an IP address, you should be suspicious."
The ‘Flashback Trojan’:
A version of an existing Trojan Horse posing as a legitimate Flash Player installer (named “Flashback.A” by a security firm) is designed to disable updates to the default Mac OS X anti-malware protection system, potentially leaving the system open to the manual installation of other malware without any system warnings. The latest Macs do not have Plash Player included. In order to prevent a potential infection with “Flashback” Trojans, Mac users should always obtain their copy of Adobe Flash Player directly from Adobe’s official website and to disable the "Open 'safe' files after downloading" option in Apple's Safari browser to avoid automatically running files downloaded from the Internet. Also, do not turn on Java in Safari Preferences/Security. Few websites use Java. Javascript is something entirely different and should be left active.
http://www.appleinsider.com/articles/11/10/19/fake_adobe_flash_malware_seeks_to_ disable_mac_os_x_anti_malware_protection.html
Flashback Trojan - Detection, and how to remove (with caution):
http://www.f-secure.com/v-descs/trojan-downloader_osx_flashback_i.shtml