Mac Security

3 Signs Your Mac Is Infected With a Virus (And How to Check)

Dan Price Updated 29-11-2019

Sadly, Macs aren’t the safe haven they once were. Yes, infections are still less common than on Windows machines, but they do happen.


If your Mac is acting kind of weird—maybe you’re seeing adverts you can’t explain or your system is unreasonably slow—the problem could be malware.

Keep reading to learn how to recognize the signs of a virus on your Mac and how to can scan your system.

What Is Mac Malware Like?

Mac malware can come in many forms. Here are some recent examples that have generated headlines:

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 of the App Store. In some cases pirated software is to blame; in others it’s software from sources that shouldn’t have been trusted.

Put simply—if you never install software from outside the Mac App Store, you don’t have anything to worry about. Sure, there are some browser-related exploits from time to time, and Java is an ongoing concern, but if macOS and browsers are up-to-date such infections are pretty unlikely.


And if you do install software from outside the Mac App Store, but are careful to research software before installing it (Googling for a review and finding an official download), you also don’t have anything to worry about.

On the other hand: if you’ve pirated Mac software or installed plugins at the request of a site offering pirated movies, you might have problems. Have you used a tainted USB drive or downloaded a sketchy email attachment? Viruses can spread in unexpected ways.

Is your Mac infected? Let’s look at the signs.

1. Unexpected Ads and Pop-Ups


Adware is becoming an ever-bigger problem on the Mac platform. If you’re seeing ads in places they previously didn’t show up, there’s a good chance you’ve installed something you shouldn’t. This is particularly true if you get 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, which is a global network of computers used for all sorts of things. If your Mac is infected, it could be helping to DDoS a website, mine Bitcoins, or any number of things that take up CPU power.

If your Mac is constantly slow, even if you don’t have any programs open, this is a possibility. And remember, if malware isn’t the problem, you need to know how to speed up your Mac 7 Common Mistakes That Slow Your Mac Down Is your Mac running slow? By changing some of your computing habits, you could improve its performance. These 7 big mistakes can slow down your Mac. Read More .

3. Malware Scanner Confirms Infection

Think your Mac might be infected? Make sure. Here are a few free programs you can use to scan your Mac and find out about any infections:

  • BitDefender Virus Scanner: This app is free. It won’t delete infections for you, but it will point out where to delete them using the Finder.
  • Malwarebytes for Mac: Malwarebytes has been one of the leading names anti-malware world for many years. Its Mac app can scan your entire system in less than 30 seconds and will remove adware and potentially unwanted programs.
  • ClamXAV: ClamXAV is the Mac version of ClamAV, a popular open source malware detection tool. It’s well worth a look.

If none of these tools come up with anything, it’s extremely unlikely that your Mac is infected. You can also use an online virus scan tool The 7 Best Free Online Virus Scan and Removal Sites Need to check for a computer virus but don't have antivirus software installed? Try these excellent online virus scanning tools. Read More . As ever, check the app reviews in the App Store to help you make a decision.

Of course, there are other apps out there—if you know of something better, let us know in the comments.

How to Check for a Virus on Your Mac?

Your Mac has defenses in place that should keep you safe from malware, though like all such measures it’s not completely foolproof. Here are a few reasons why you don’t need to worry (much):



Gatekeeper stops uninformed users from installing potentially unsafe software.

By default, this means anything not from the Mac App Store, but you can also configure it to block apps from unknown developers. Of course, many Mac users disable Gatekeeper completely so they can run whatever software they like, including things they’ve compiled themselves. The hope is that well-informed users will research the apps they run before installing it.


Apps installed through the Mac App Store have very limited access to the broader system, a limitation intended to stop one app from messing up your entire system.


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

Part of OS X since 2009, this program isn’t like Windows anti-viruses—it’s completely invisible to most users. You can’t open the program and run a scan yourself, and you can’t manually install updates. But if you’re infected with a known virus, odds are this program will eventually notify you. It also stops you from opening infected files.

Recommended Mac Antivirus Apps

You should now recognize whether your Mac has been infected with malware. However, prevention is nine-tenths of the cure, as they say.

If you want to make sure you never have to worry about malware on Mac, you should install a high-quality Mac antivirus suite The 7 Best Truly Free Antivirus Software for Mac Viruses and security issues abound, even on Mac. It's critical that you use a free antivirus for Mac, no matter how smart you are. Read More . And you can also use these helpful link checkers to make sure that sites are safe 7 Quick Sites That Let You Check If a Link Is Safe Before clicking a link, use these link checkers to check that it doesn't lead to malware or other security threats. Read More before you put your Mac in danger.

Related topics: Anti-Malware, Botnet, Software Piracy.

Affiliate Disclosure: By buying the products we recommend, you help keep the site alive. Read more.

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  1. Kar
    August 20, 2017 at 6:40 pm

    Hypothetically, say a few months ago I snooped around on a pirate site, and may or may not have clicked a link by accident.
    Say, if, now, randomly, my safari field were to go gray, and a popup appear with a phone number, etc, saying, let's say, my computer had been infected with something, let's just say it said "trojan" and then my entire search history was changed to "Error" or something like that, what, hypothetically, would I do?

  2. Chu Nguyen
    January 24, 2017 at 7:25 pm

    Thank you, it is wonderful to know it!

  3. mj lee
    December 22, 2016 at 5:53 pm

    It isn't good when the article recommends virus checkers that could be harmful to users. Of the 3 Malware Scanners mentioned in section 3 of this article,
    the first goes to some russian site
    the second and third packages are not on the apple app store
    the third package seems to not really be supported

    If you can't keep an article up to date, it should be deleted rather than steer users to bad sites.

  4. Anonymous
    April 28, 2016 at 6:54 am

    Let me start out by stating that I am not a Mac user. However, please note that this is not some part of the Mac vs. Pc war, I just don't need one. In addition, computers are tools and you use the right tool for the job.

    Against popular (put horribly incorrect) belief, the Mac OS is NOT immune to viruses, spyware, or any sort of malware for that case. So yes, you can get spyware on your Mac. The reason why so many egotistical Mac users have decided to tell uninformed users that there are no bugs for Mac, is because there are significantly less than Windows OS. Malware writers, as well as script kiddies, want to target the largest population, so they take out Window's boxes.

    On the other hand, UNIX kernels, which is what Macs are based off of, as are Linux distros, is, in my opinion, more secure than the Window's equivalent.

    At any rate, on to your question. There are anti-virus, etc. programs for Mac. GET ONE. I routinely run Linux, and while it has little malware, I still run an AV. You can tell that you have some sort of a bug if just random things start happening. If your computer is running extremely slow, check the processes (Not sure how on Mac, ps -A on Linux, so may be the same) and see if any of them seem suspicious. While most of the times a keylogger will not be called keylogger.exe, there are a lot of novice script-kiddies out there. If you see a lot of TCP or UDP connections (maybe netstat?) on strange ports, that could be a sign. Also, if you see any data being moved along port 0, that could be a problem. But most importantly, run your AV. I know that there are some free ones out there. I know that McAffee (I think) or one of the major companies has started making a mac Av, so you might consider it.

    Sorry for the long run on. Email me if you need anything and Good Luck.

    • eric
      July 22, 2019 at 6:29 am

      I have been using a imac for about 5 years.Before that like most people i was on Windows and Linux as well.I am not a "egotistical " mac user as you described it.No operating system is 100 percent fool proof.Having said that i have never had a issue with malware on my mac.Of course i don't download from shady sites,use torrents to download shady material or open links from e-mail sources i do not know.I do not run anti-virus in real time.That would require allowing another kernel extension and the fewer the better.I do run a stand alone av (bit defender) from the the app store and manually scan downloads.Very occasionally it will flag a download for a trojan or adware bundled program.Bundled installers are a huge problem.Last but not least i see the fake adobe flash update scam and wonder why people fall for it.Anyway that has been my experience but am always vigilant.p.s no way in hell is McAfee going on my mac.

  5. ben
    April 25, 2016 at 6:22 pm

    my system get hot in no time when running lightroom and photoshop, sometimes only the safari, is my system infected?i'm on macbookpro 15'' retina

  6. Rhonda Huot
    April 4, 2016 at 8:54 pm

    I'm trying to use malwarebytes on a google browser as I keep having something trying to download when I use safari. I don't know what I'm doing wrong as it shows that it is in my applications folder but won't let me eject or even run the program. I feel like I'm missing a step in the installation but have done everything the instructions say. Any help?

  7. Joe
    March 17, 2016 at 8:14 pm

    Does Webroot scan for all of these?

    • Justin Pot
      March 22, 2016 at 1:40 pm

      I can't find evidence of Webroot working on Mac at all, but I could be wrong.

  8. Dame
    January 20, 2016 at 9:27 pm

    Sooo...hypothetically speaking of course, say I did download software from The Pirate Bay and it's causing said hypothetical Mac to slow a little. What would I do in that scenario? What would I have to download in order to get rid of any infections?

  9. Grace
    December 1, 2015 at 6:14 pm

    I've tried everything and my problem has not been solved. I keep seeing popups on my browser, usually when I'm being redirected by a link. They are all from Mackeeper, and they all force me to quit Safari. I did not install anything on my computer, other than Adobe. I've searched everywhere for a way to keep the ads from appearing, but I have not found a solution yet. I downloaded and installed Malwarebytes but it has not found anything. I've followed instructions that said to delete certain files from the Library, but I don't have any of the ones mentioned. I've tried switching networks and the problem just won't go away.

    • Justin Pot
      December 1, 2015 at 6:18 pm

      Hey Grace, if you switch your browser does the problem happen there too? Download Firefox and try it out. If the ads don't pop up there, I'd suggest checking your Safari extensions and seeing if anything familiar is there.

      Sorry this is happening to you, that's frustrating.

      • Grace
        December 1, 2015 at 6:23 pm

        I don't have any Safari Extensions, but I'll try downloading Firefox.

    • CHRiS
      June 2, 2016 at 3:09 am

      Omg do not install mackeeper it is and adware virus it

    • CHRiS
      June 2, 2016 at 3:11 am

      just get rid of mackeeper it is all adware and will not go away untill you get rid of mackeeper and you can gooogle how to get rid of it.

  10. Nicole
    November 24, 2015 at 9:14 pm

    this worked for me thank you so much :)

  11. Anonymous
    October 19, 2015 at 11:15 pm

    I was having pop up's out of no where. It was hell. I used the AdwareMedic and it fixed everything. Thanks so much for this information.

    • Justin Pot
      October 20, 2015 at 12:03 am

      I'm so glad this article was helpful for you!

  12. Anonymous
    August 15, 2015 at 5:03 pm

    Did you know that there is now Malwarebytes For Mac?

    • Justin Pot
      August 15, 2015 at 5:52 pm

      I do! I've tried it out, runs quickly. And it seems like they've hired the blogger behind The Safe Mac, which bodes well

  13. Lad
    May 23, 2015 at 4:51 pm

    Thank you very much Justin, I used AdwareMedic and it helped. Then I donated them of course. It is very frustrating constantly getting those "wasps"- adds. But now my new mac book pro is fast again.

    • Justin Pot
      May 23, 2015 at 7:30 pm

      I'm glad you got it all tuned up!

  14. Grant R.
    December 3, 2014 at 3:48 pm


    Good morning! I removed 2 different Mac viruses in my first six months (I remember because it surprised me so much), and I was only put in charge of about 30 Macs. I wouldn't call them common, but they are just as easy to get and they're just as bad. Go to a shady website, or stick in a flash drive from a co-worker and whammo, you're infected.

    The best way to describe it is the two "S" words: MacOS is safer, but not more secure. Safer in the odds - they are far lower you'll contract a virus... but not any more secure in that when a virus wants to get in, it most certainly will (assuming you are not protected).

    Check out Apple's very own security updates page:

    Often, they release security updates several times a month. That should tell you something about the current and active status of malware on the Mac. Hope that helps! Stay safe out there.

  15. Paul
    December 3, 2014 at 2:48 pm

    Having worked in both PC-centric and MAC-centric enterprise environments, I agree that the PC is decidedly more prone to infection than the Mac *** HOWEVER *** the existence of Macintosh platform viruses going (way) back to SevenDust and the AutoStart worm support the premise that ANY device (including Linux systems) connected to the Internet or to a network which has an active Internet connection needs to have some sort of active malware protection...

    • Justin Pot
      December 3, 2014 at 8:01 pm

      You're right! I didn't mean to say that viruses aren't possible, or even likely, just that if you're having trouble with your Mac the problem is usually something else. But I really appreciate you taking the time to point out that I may have underplayed malware's role, and I hope it's a useful resource to fellow readers.

      Have a great day, okay?

  16. Grant R.
    December 2, 2014 at 9:01 pm

    I think that telling Mac owners they "probably aren't" infected is not wise. I was a consultant for a Mac-only IT company, and I personally removed viruses from Macs during that time. They are computers. They are no different from any other computer in that they are susceptible to viruses through all of the same channels... including websites, external storage, email, and local area networks. Merely sticking to software downloads from the App Store is not enough to protect you. If you own a Mac, please get and use a good AV product!

    (To add to Justin's list, ESET also makes a decent Mac AV product.)

    • Justin Pot
      December 3, 2014 at 2:31 pm

      How common were Mac viruses in your experience? I also worked IT and never really ran into any (but did run into a few antivirus apps that made things unstable), but it's been a few years. Is it possible I'm a little out of date?

    • Robert Drake
      February 26, 2015 at 3:44 pm

      is this Richard?

  17. Bud
    November 27, 2014 at 3:42 pm

    Thanks for this info. here. Always good to know and to be updated.

  18. Doc
    November 26, 2014 at 11:28 pm

    You've completely forgotten the Flashback trojan, which infected more than 600,000 Macs through flaws in Java. Months later, 50,000 machines were *still* infected.

    • Justin Pot
      November 29, 2014 at 2:36 pm

      I was just giving a few examples, and tried to only pick recent ones. I wasn't trying to give a complete list of every piece of Mac malware; that would be longer than a lot of people realize.