How to Scan Your Mac for Viruses, Malware and Spyware

This detailed guide will show you how to install, configure and use free software to scan your Mac for viruses, malware and spyware.

Security Software for macOS

I’ll keep this introduction brief. Here’s how I feel about Mac security software –

If you have critical, can’t-live-without stuff on your Mac, it’s worth paying for security software. None of the free apps offer complete coverage. This guide uses the free version of Avast Security – which includes a full antivirus/malware scanner. However, the free version does not offer ransomware protection. Ransomware on a Mac is still quite rare, but it does happen, and if you regularly install software that doesn’t come from the Mac App Store the odds of being infected go up.

If you’re going to shell out your hard earned money, I would recommend Bitdefender Antivirus for Mac. It offers more features than Avast and it’s less expensive.

With all of that said – if what you’re looking to accomplish is to scan your Mac for viruses and malware, Avast (and this guide) is for you.

Installing & Setting Up Antivirus Software

  1. Installing and setting up Avast isn’t particularly complicated, it’s just a bit more involved than a regular “drag to the Applications folder” type of installation. Start by downloading the installer file. Once the download has completed, open the .DMG file and double-click Install Avast Security.pkg
  2. Avast Security for Mac installer file

  3. Click the Allow button when asked if program can be run to determine whether Avast will work on your Mac.
  4. a confirmation panel in macOS

  5. If you’re using macOS Catalina or Big Sur, you’ll get a warning message about a System Extension being blocked. Click the Open Security Preferences button when you see that message.
  6. System Extension warning message

  7. This will open the Security & Privacy section of the System Preferences. Click on the ‘lock’ icon in the bottom left corner and enter your password when prompted. Then, click the Allow button next to the System software message (see screenshot below).
  8. Security and Privacy section of the macOS System Preferences

  9. During the installation, you may be asked if you’d like to install Google Chrome. You do not need to install it, and can skip that step entirely.
  10. If you’re asked to allow Avast permission to access your Downloads folder, click the OK button.
  11. an arrow pointing at an OK button

  12. After you click “Next” a bunch of times, click the Close button on the last of the installation screens.
  13. the last installation screen for Avast Security for Mac

  14. With the installation complete, now it’s time to setup and configure Avast – which mostly consists of granting various permissions. To gets started, click the CONTINUE button.
  15. setup Avast for Mac

  16. Click the OPEN CONFIRMATION DIALOG button.
  17. an arrow pointing to a button titled open confirmation dialog

  18. Click the ALLOW button.
  19. an arrow pointing to an Allow button

  20. Confirm that it says DONE! above the CONTINUE button, and then click that same CONTINUE button.
  21. continue setting up Avast

  22. Avast needs to be able to access all the files on your Mac so that it can scan them, which means it needs to be granted full disk access. Click the OPEN SYSTEM PREFERENCES button.
  23. an open system preferences button

  24. This time the Privacy & Security window will open up with the Privacy tab displayed. If it isn’t already selected, click Full Disk Access from the column of options on the left side of the window. Place a check in the box next to Avast Security
  25. the Privacy section of the macOS Privacy & Security System Preferences

  26. A message will pop up letting you know that Avast won’t have those access permisions until it has been restarted, so click the Quit & Reopen button.
  27. a confirmation dialog box with an arrow pointing to the Quit & Reopen button

  28. Avast will close down and reopen itself. When it’s open again, you’ll probably see a big “This Mac is not fully protected” message. No problem. Click the Core Shields button.
  29. the Avast Security App home screen with one of the Core Shields disabled

  30. Toggle the File Shield switch from OFF to ON
  31. a toggle on/off switch

  32. Confirm that all 3 “core shields” have been turned on, and then click the ‘back arrow’ located in the upper-left corner of the Avast window.
  33. the Avast App screen with all 3 Core Shields enabled

Check Your Mac for Viruses, Spyware & Malware

  1. Now let’s scan your Mac for viruses, malware and/or adware. Click the RUN SMART SCAN button now.
  2. starting a scan for mac viruses

  3. Avast will do a quick check to make sure you have the very latest virus definitions installed and everything is completely up to date.
  4. installing latest virus definitions

  5. Once it’s done, click the NEXT button.
  6. a Next button

  7. The actual scan can take a while – the length of time is determined by the number of files you have and the overall speed of your Mac. It’s probably a good time to go grab a cup of coffee or tea.
  8. the process of a scan for Mac viruses

  9. With a bit of luck, hopefully nothing was found. If that’s the case, click the Next button. If Avast did identify something bad, follow the steps it suggests in order to remove any infected files.
  10. a completed virus scan in macOS

  11. This part of the ‘scan’ is an upsell. Avast wants you to buy their software so you’re completely protected, but again – if you’re going to pay for security software, I recommend Bitdefender Antivirus for Mac over Avast.

    Click the Skip for now link in the bottom-right corner of the Avast window.

  12. an arrow pointing at a link titled Skip for now

  13. Click the Done button.
  14. a Done button

  15. There is one set of settings you may wish to change – click the Menu button in the top-right corner of the Avast window, and select Preferences from the list of options.
  16. the Avast Security menu options

  17. Choose the Scans tab. The options you may wish to change (they’re disabled by default) are: Scan whole files, Scan all Time Machine backups, and Scan archives. Each of these items will increase the time it takes to scan your Mac, but the scan will be even more comprehensive. Just let it run overnight if time is a concern.
  18. advanced options for when you scan a Mac for viruses

  19. That’s it! Your Mac is that much safer now :)

If this guide helped, be sure to check out our other Mac content.

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