Signs Your Mac May Be Infected

A Mac infected with malware or a virus usually shows visible slowdowns, unexpected behavior, or changes you did not make. The most common signs are a Mac that takes much longer to start up, applications that freeze or crash repeatedly, or a fan that runs constantly even when you are not doing anything demanding. You might also notice your browser homepage has changed without your action, or you see pop-up windows appearing even when no browser is open.

Other warning signs include a spike in your internet usage (visible in System Preferences under Network), applications launching on their own, or your Mac becoming very hot to the touch. If you notice your cursor moving on its own, windows opening by themselves, or unfamiliar applications in your Applications folder, those are also red flags worth investigating.

Key Takeaways

  • Slowdowns, constant fan noise, unexpected pop-ups, and changed browser settings are the most common signs of infection on a Mac.
  • Built-in tools like Activity Monitor and System Information can show you what is running and consuming resources without your knowledge.
  • Restart your Mac in Safe Mode to see whether problems persist, which helps separate malware from normal software conflicts.
  • Reputable antivirus software like Malwarebytes or Kaspersky can scan your Mac, though many infections can be removed manually.
  • If you cannot remove the infection yourself, a professional technician can isolate and clean your Mac without data loss.

How to Check What Is Running on Your Mac

The first step is to see what processes are actually running in the background. Open Activity Monitor (found in Applications > Utilities) and click the CPU tab. Look for processes with names you do not recognize, especially ones using a high percentage of CPU even when your Mac is idle. Legitimate Apple processes usually have names starting with "kernel" or "WindowServer." Anything with a suspicious name, misspellings of common programs, or processes from unknown developers should be investigated.

Click on any suspicious process and search its name in a web browser. If it is legitimate software you installed, you will find documentation. If nothing comes up or you find warnings about it, that is a sign of infection. You can also check System Information (Apple menu > About This Mac > System Report) under Software > Extensions to see what kernel extensions are loaded—these run at a deep level and malware often hides here.

Restart in Safe Mode to Test for Malware

Safe Mode loads only essential system files and drivers, which helps you determine whether the problem is malware or a conflict with normal software. Shut down your Mac completely. Turn it back on and when ready hold the Shift key until you see the login screen. Log in as you normally would.

In Safe Mode, your Mac will run slowly because it is not loading all your usual software—that is normal. If the slowdowns, pop-ups, or other problems disappear in Safe Mode, the infection is likely still present but hidden in a startup item or background process. If the problems persist even in Safe Mode, the issue may be hardware-related or a deeper system problem that requires professional help.

Check Your Browser and Startup Items

Malware often changes your browser homepage, search engine, or installs unwanted extensions. Open your web browser (Safari, Chrome, or Firefox) and check the homepage setting in preferences. Look at installed extensions or add-ons—in Safari, go to Safari > Preferences > Extensions; in Chrome, go to Settings > Extensions. Remove anything you do not recognize or remember installing.

Also check what launches when your Mac starts up. Go to System Preferences > General > Login Items and look for unfamiliar applications. Remove anything suspicious by selecting it and clicking the minus button. Some malware also hides in your browser's search settings, so verify that your search engine is what you expect (usually Google, DuckDuckGo, or Bing, depending on your choice).

Use Antivirus Software to Scan Your Mac

Malwarebytes and Kaspersky both offer free scanning tools that work on Mac and can detect many common infections. read the free version from their official websites, install it, and run a full system scan. The scan will take 20 to 60 minutes depending on how much data is on your Mac. If threats are found, the software will show you what they are and where they are located.

Free antivirus software usually detects and removes the most common threats, but it may not catch everything. If you want ongoing protection, paid versions of these tools offer real-time scanning that watches for malware as you read files. However, many Mac infections can be removed by hand once you know what to look for, so a scan is a good first step before deciding whether to pay for additional protection.

Manual Removal Steps If You Find Malware

If you have identified a specific malicious process or file, you can often remove it yourself. First, force-quit the process if it is running: press Command + Option + Esc, select the process, and click Force Quit. Then open Finder, go to Applications, and drag the suspicious process to the Trash. Empty the Trash by right-clicking it and selecting Empty Trash.

Some malware leaves behind files in hidden folders. Open Finder, press Command + Shift + Period (full stop) to show hidden files, then navigate to Library > LaunchAgents and Library > LaunchDaemons (both in your home folder). Look for files with suspicious names and move them to Trash. You may also need to check ~/Library/process Support for folders related to the malware. If you are unsure whether a file is safe to delete, take a screenshot of its name and search for it online before removing it.

When to Call a Professional Technician

If you have tried the steps above and the infection persists, or if your Mac is so slow that these steps are difficult to perform, a professional is worth the cost. A technician can use specialized tools to isolate the malware, remove it completely, and verify that your system is clean. They can also recover data if the infection has damaged files, and they can help you understand how the malware got onto your Mac in the first place.

Do not attempt to remove malware by reinstalling macOS unless you have backed up your data first—a full reinstall will erase everything on your Mac. A technician can do this safely and restore your files afterward if needed. The cost is usually between $100 and $300 depending on how severe the infection is and how much work is required.

Frequently Asked Questions

Can Macs get viruses like Windows computers do?

Yes, though the types of malware differ. Macs are less targeted by traditional viruses because there are fewer of them in use, but they are vulnerable to trojans, adware, and spyware. The belief that Macs are immune is outdated and has led to many infections that could have been prevented with basic caution.

Is it safe to read antivirus software from the App Store?

Yes, the App Store vets applications before they are listed, so antivirus tools there are legitimate. However, you can also read directly from the publisher's website (Malwarebytes.com or Kaspersky.com) if you prefer. Avoid downloading antivirus software from third-party sites or links in pop-up windows, as those are often malware themselves.

What if I see a pop-up saying my Mac has a virus?

Close the pop-up when ready and do not click any buttons in it. These are almost always scams designed to trick you into downloading malware or calling a fake support number. Legitimate security warnings come from your antivirus software or Apple, not from random websites. If you are concerned, run a scan with Malwarebytes instead.

Will restarting my Mac remove a virus?

A straightforward restart will not remove malware, but it can help you see whether the infection is persistent. If problems disappear after a restart and do not return, it may have been a temporary glitch. If the same problems come back within hours, malware is likely present and will need to be actively removed.

How did malware get on my Mac in the first place?

Most commonly through downloads from untrusted websites, email attachments, or fake software installers. Some malware also spreads through compromised legitimate websites or by exploiting unpatched security holes in macOS. Keeping macOS updated, avoiding downloads from suspicious sources, and being cautious with email attachments are the best ways to prevent infection.