Before i start can i remind everyone not to flame because were talking about macs
Ok so if your a mac user that thinks your OS is immune to viruses and/or there extreamly rare and u do not need to install anti viruses and that macs OSes are the most secure thing in the world!
Think AgainHow to remove Mac Defender.Removal steps
Move or close the Scan Window
Go to the Utilities folder in the Applications folder and launch Activity Monitor
Choose All Processes from the pop up menu in the upper right corner of the window
Under the Process Name column, look for the name of the app and click to select it; common app names include: MacDefender, MacSecurity or MacProtector
Click the Quit Process button in the upper left corner of the window and select Quit
Quit Activity Monitor application
Open the Applications folder
Locate the app ex. MacDefender, MacSecurity, MacProtector or other name
Drag to Trash, and empty Trash
Malware also installs a login item in your account in System Preferences. Removal of the login item is not necessary, but you can remove it by following the steps below.
Open System Preferences, select Accounts, then Login Items
Select the name of the app you removed in the steps above ex. MacDefender, MacSecurity, MacProtector
Click the minus button
Use the steps in the “How to avoid installing this malware” section above to remove the installer from the download location.
Note: Apple provides security updates for the Mac exclusively through Software Update and the Apple Support Downloads site. User should exercise caution any time they are asked to enter sensitive personal information online.
For the full artical and the source look at
http://support.apple.com/kb/HT4650