Unfortunately, Macs are no longer the safe haven they used to be. Yes, infections are still less common than on Windows computers, but they do happen.

If your Mac is acting a little strange – you might see ads that you can't explain, or your system is inappropriately slow – the problem could be malware.

Read on to learn how to spot the signs of a virus on your Mac and scan your system to find it.

Can Macs Get Viruses?

Despite the seemingly widespread belief that Macs are immune to viruses, they can still be infected.

In fact, Mac malware can come in many forms. Here are a few examples that made headlines:

  • Silver Sparrow: Silver Sparrow targets Macs with an M1 chip. It uses the macOS Installer's JavaScript API to execute commands and is known to contact its servers once an hour. Experts fear that a major attack will be prepared in the near future.
  • Pirri / GoSearch22: The first malware to target M1 Macs was Pirri / GoSearch22. The virus itself is adware. It inserts ads in places where they wouldn't normally appear.
  • ThiefQuest: First seen in 2020, ThiefQuest steals data from files in folders on your computer. The malware itself is disguised as ransomware unless a ransom is never asked for.
  • LoudMiner: This malware is malicious crypto mining app. It was distributed via a cracked version of the popular Ableton Live app.

How do you know if your Mac was infected with a virus?

All of these infections have one thing in common: They infect Macs through processes outside the App Store. In some cases, piracy is to blame; In other cases it is software from sources that should not have been trusted.

Put simply, if you never install software from outside the Mac App Store, then you don't have to worry. Sure, there are some browser-related exploits from time to time, and Java is a constant problem, but with macOS and browsers up to date, such infections are pretty unlikely.

And if you're installing software from outside the Mac App Store but carefully researching software (Googling for a review and find an official download) before installing, then you don't need to worry either.

On the other hand, if you've pirated Mac software or installed plugins at the request of a pirated website, you might run into problems. Did you use a faulty USB drive or downloaded a sketchy email attachment? Viruses can spread in many unexpected ways.

So is your Mac infected? Let's look at the signs.

1. Unexpected ads and popups

Interesting secret. New malware being triggered on ~ 30,000 Macs? Once an hour, the Macs turn to a control server to look for commands from attackers. So far, however, no user data has been supplied. Malware has a self-destruct function, but attackers did not initiate it. https://t.co/JmdXuIkEc2

– Kim Zetter (@KimZetter) February 20, 2021

Adware is becoming a growing problem on the Mac platform. If you're seeing ads in places where they weren't shown before, there's a good chance you've installed something that you shouldn't. This is especially true if you're getting pop-up ads even when you're not browsing the internet.

2. Your Mac is slow for no reason

Some Mac malware makes your Mac part of a botnet, a global network of computers used for all sorts of purposes. If your Mac is infected, it can help launch a Distributed Denial of Service (DDoS) attack on a website, mine bitcoins, or do any number of tasks that consume CPU power.

If your Mac is consistently slow even when no programs are running, this is a possibility. And remember, if malware isn't the problem, you need to find out why your Mac is running slow.

3. Malware scanner confirms infection

Do you think your Mac might be infected? It's time to check. Here are some free programs you can use to scan your Mac and find out about infections:

  • Bitdefender virus scanner: This app is free. It won't clear infections for you, but it will point out where to use Finder to clear them.
  • Malwarebytes for Mac: Malwarebytes has been one of the leading names in the anti-malware world for many years. The Mac app can scan your entire system in less than 30 seconds and remove adware and potentially unwanted programs.
  • ClamXAV: ClamXAV is the Mac version of ClamAV, a popular open source tool for malware detection. Well worth a look.

If none of these tools provide anything, it is extremely unlikely that your Mac is infected. You can also use an online virus scanning tool. As always, check the app ratings on the App Store to make a decision.

Of course, there are other apps too – if you know anything better, let us know on Twitter.

Related: The Best Free Antivirus Software

Here's how to check for a virus on your Mac

Your Mac has protections designed to keep you safe from malware. However, like all of these measures, they are not completely foolproof. Here are some reasons why you shouldn't worry:

goalkeeper

macOS will continue to be blocked.

Gatekeeper's default setting only allows Mac App Store apps and apps signed by Developer ID.

Apps will soon have to be notarized in order to pass upcoming gatekeeper exams.

Apple implements a whitelist for the MacOS app (cryptographic).

– Stephen Hoffman (@HoffmanLabs) December 4, 2018

Gatekeeper prevents uninformed users from installing potentially unsafe software.

By default, this means anything that isn't from the Mac App Store. However, you can also configure it to block apps from unknown developers. Of course, many Mac users disable Gatekeepers entirely so they can run whatever software they want, including things they've compiled themselves. The hope is that well-informed users will examine the apps they are running before installing them.

Sandboxing

Apps installed through the Mac App Store have very limited access to the broader system. This limitation is to prevent an app from messing up your entire system.

Related: Reasons Macs Are Less Likely to Get Malware Than Windows

XProtect

XProtect is the anti-malware program you didn't know you had.

This program has been part of the Mac operating system since 2009 and is no different from Windows antivirus programs. It is completely invisible to most users. You cannot open the program and run a scan yourself, and you cannot install updates manually. However, if you are infected with a known virus, this program will likely notify you. It also prevents you from opening infected files.

If that doesn't work, try one of these great paid Mac antivirus apps.

Recommended Mac antivirus apps

You should now see if your Mac has been infected with malware. However, prevention, as they say, is nine tenths of a cure. If you want to make sure that you don't have to worry about malware on a Mac, consider installing a good quality Mac antivirus suite.

Once you have a solid antivirus app running (and assuming that you make an effort to be safe online), the chances are that you will ever run into Mac malware on your own computer.

5 easy ways to infect your Mac with malware

Malware can definitely affect Mac devices! Avoid these errors or your Mac will be infected.

Continue reading

About the author

Dan Price
(1563 articles published)

Dan joined MakeUseOf in 2014 and has been the partnership director since July 2020. Contact him for information on sponsored content, affiliate agreements, promotions, and other forms of partnership. You can also find him in the showroom every year at CES in Las Vegas. Say hello when you leave. Prior to his writing career, he was a financial advisor.

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