Viruses in the computer world (most of which won’t affect your Mac anyway) have given rise to a new class of malware called “scareware”. In short, this type of app tries to frighten you into purchasing a product you don’t need to fix problems that don’t exist.

Here’s how it works: You’re minding your own business visiting some web site when, suddenly, a page pops up that looks like a standard Mac window warning you of a variety of problems. It urges you to click a link to perform a “free” scan and, before you know it, you’ve installed something you can’t seem to get rid of without paying for it. In short, it’s a hoax designed to separate naturally nervous users from their cash.

Enter “Mac Defender”.

Mac Defender (a/k/a Mac Protector, and probably some other name soon) is just such an application. If you are tricked into installing it, the method for removing it is not obvious. Fortunately, it’s not hard either. You can find detailed instructions with pictures here, but these are the steps:

  • Close the Mac Defender window if it’s open.
  • Navigate to your /Applications/Utilities/ folder. The easiest way is to click anywhere on your desktop, then go up to the Go menu and choose “Utilities”.
  • Start Activity in your Utilities folder.
  • If no window appears, go up to the Window menu and choose “Activity Monitor”.
  • In the window that appears, look in the upper, right corner and you will see a search box. Type “Defender” there.
  • “MacDefender” should appear in the list in the main part of that window. Highlight it and press the red “Quit Process” button in the toolbar.
  • Choose “Force Quit” from the window that appears.
  • Quit Activity Monitor.
  • Navigate to your /Applications/ folder and trash Mac Defender.
  • Go to your Apple menu and choose “System Preferences”.
  • Click on the “Accounts” icon, then click the “Login Items” tab.
  • Locate “Mac Defender” in the list and press the “-” button beneath the list.

To be clear, this is not a virus because it can only get onto your machine with your knowledge and, in fact, your permission. The lesson is, don’t believe everything you see on the web, be skeptical about stuff that tries to scare you into doing something, and be conscious and particular about what you decide to install.