To remove it, here’s what you need to do….
- Firstly, you need to close the program by clicking the red button.
- Next go to Utilities, double click on Activity Monitor.
- Select MacDefender and click Quit Process. And if it ask you if you are sure you want to quit, click Force Quit!
- Click Go again and go to Applications. Right click on MacDefender and choose Move to Trash.
- Then click on Apple Menu, select System Preferences and under the System category select Accounts options. On the Account screen, click Login items, highlight MacDefender and click the minus sign at the bottom!
- Finally, start Safari program, click the menu options and choose Preferences. Click the General button and uncheck Open ‘safe’ files after downloading.
Source: Bleeping Computer