You can protect your Mac from malware by only allowing apps that come from the App Store or from identified developers.
- From the Apple menu in the top left of your screen, Open System Preferences
- Click Security & Privacy, then the General Tab
- Click the golden padlock in the lower left to enter your Mac's login credentials
- Click the button next to "App Store and identified developers"
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App Store: Select to allow only apps that have been downloaded from the App Store.
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App Store and identified developers: Select to allow apps only from the App Store, and from developers identified by Apple.