For those infected with the MACDefender malware, the following steps are recommended:
1. Open Applications > Utilities > Activity Monitor and quit any processes linked to MACDefender.
2. Delete MACDefender from the Applications folder.
3. Check System Preferences > Accounts > Login Items for suspicious entries
4. Run a Spotlight search for "MACDefender" to check for any associated files that might still be lingering.
There are several varients so change MacDefender to whichever name is being used.