OS X El Capitan: The Missing Manual

Gatekeeper

This security feature sends Eastern European teenage hackers into therapy.

Nasty programs aren’t very common on the Mac to begin with. But now, unless you turn Gatekeeper off, downloading a program that’s secretly designed to damage your Mac is virtually impossible.

Gatekeeper won’t even let you install programs that haven’t been proved to be safe (Figure 11-12).

There’s no Gatekeeper app or even a Gatekeeper System Preferences icon. Instead, to find Gatekeeper, you open System Preferences→Security & Privacy→General. At the bottom of this screen (Figure 11-12, top), you see three options. These three humble buttons are Gatekeeper.

Click the and enter your password to unlock this panel. Here your choices, under “Allow apps downloaded from”:

• Mac App Store. This is the safest option. Every program that Apple allows into its Mac App store is safe. Each has been tested by Apple to make sure that, among other things, it’s both sandboxed (blocked from accessing parts of the Mac that it doesn’t need) and digitally signed (set up to notify that Mac if it’s been altered in any way since it left the software company).

  

  Figure 11-12. Top: The “Allow apps downloaded from” options are, in fact, the face of Gatekeeper. Bottom: If you try to open a downloaded program that Apple can’t vouch for, ...