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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:
- OSX/Dok Malware: The OSX/Dok malware is one of the most dangerous Mac viruses seen in the wild. It is spread via a ZIP file email attachment. If run, it replaces the “AppStore” Login Item with itself, allowing it to run every time the system boots. The malware will then prompt you for your admin password, giving it control over your system’s admin rights. Its end goal is to route web traffic through proxy servers so it can impersonate sites.
- Meltdown and Spectre: Mac computers were left vulnerable from the Meltdown and Spectre flaws found on Intel chips in early 2018. The bugs allowed a hacker to steal data by using a rogue data cache load.
- OSX/MaMi: 2018 also saw the arrival of OSX/MaMi. It let hackers install a new root certificate and hijack the DNS servers, giving them a way to perform “man-in-the-middle” attacks.
- OSX/Pirrit: In 2016, OSX/Pirrit was discovered. It was hidden in pirated versions of Microsoft Office and Adobe Photoshop. It could access root privileges and automatically install more software.
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
Multiple new pieces of #Mac #malware have appeared in December, all distributed through different means, but all opening backdoors on infected computers: https://t.co/n3pAQo1JIX by @thomasareed #cybersecurity #infosec #Apple
— Malwarebytes (@Malwarebytes) December 11, 2018
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.
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. 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):
macOS is getting further locked down.
The Gatekeeper default setting allows only Mac App Store apps and apps signed by Developer ID.
Apps will soon have to be notarized to pass upcoming Gatekeeper checks.
Apple is implementing a macOS app (cryptographic) whitelist.
— Stephen Hoffman (@HoffmanLabs) December 4, 2018
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. And you can also use these helpful link checkers to make sure that sites are safe before you put your Mac in danger.