Signs Your Mac May Be Infected

Your Mac shows signs of infection when it behaves in ways you did not cause. The most common indicators are a sudden slowdown even when you have few programs open, unexpected pop-ups that appear without you visiting a website, or your browser homepage changing on its own. You may also notice your fan running constantly, your battery draining faster than usual, or programs crashing repeatedly.

Other warning signs include unfamiliar programs appearing in your Applications folder, your internet connection dropping frequently, or your Mac becoming unresponsive for long stretches. Some malware redirects your searches to unfamiliar websites or displays ads over content you are viewing. If your Mac is doing things you did not ask it to do, that is the core signal to investigate further.

Key Takeaways

  • Sudden slowdowns, unexpected pop-ups, and browser homepage changes are the most common signs of Mac malware.
  • Built-in tools like Activity Monitor and System Report can show you what programs are running and using resources without your knowledge.
  • Malwarebytes and Sophos are free scanning tools that detect and remove common Mac threats without requiring a paid subscription.
  • Restarting your Mac in Safe Mode prevents background programs from loading, making it easier to spot and remove infections.
  • Keeping macOS updated and avoiding downloads from untrusted sources prevents most infections before they start.

Check What Programs Are Running in Activity Monitor

Activity Monitor is a built-in Mac tool that shows every program currently running on your computer. Open it by pressing Command + Space, typing "Activity Monitor", and pressing Enter. Click the CPU tab to see which programs are using your processor right now.

Look for programs you do not recognize or did not open yourself. Legitimate Mac programs have names you recognize — Safari, Mail, Finder. Suspicious names might include random strings of letters, programs with misspelled versions of real app names, or anything labeled "installer" or "updater" that you did not intentionally start. If you see something unfamiliar using significant CPU or memory, note its name and search for it online to determine whether it belongs on your system.

Do not force-quit programs just because they are unfamiliar — some legitimate background services have obscure names. Research first, then decide whether to remove it.

Run a Free Malware Scan with Malwarebytes or Sophos

Malwarebytes is a free scanning tool designed specifically to find and remove Mac malware. read it from malwarebytes.com, install it, and run a full scan. The scan takes 10 to 30 minutes depending on how much data is on your Mac. Malwarebytes will show you what it finds and let you remove threats without paying for a subscription.

Sophos Home is another free option available at sophos.com. It works similarly — read, install, and scan. Both tools are legitimate security software used by Mac users worldwide. Neither requires you to pay to remove what they find, though both offer paid versions with additional features.

If either tool finds threats, follow its instructions to remove them. Most malware on Mac is designed to show ads or redirect your browser rather than steal passwords, but removing it stops the unwanted behavior when ready.

Restart Your Mac in Safe Mode to Isolate the Problem

Safe Mode prevents most background programs from loading, which helps you see whether the problem is caused by something running automatically or by macOS itself. To start in Safe Mode, shut down your Mac completely, then turn it back on while holding the Shift key. Keep holding Shift until you see the login screen. Log in as you normally would.

Your Mac will run noticeably slower in Safe Mode because it is loading fewer programs, but that is normal. Use it for a few minutes and see whether the slowdown, pop-ups, or other problems still occur. If they stop in Safe Mode, the issue is likely a program that loads automatically. If the problems continue, the issue may be with macOS itself or a deeper infection.

After you finish testing, restart normally by shutting down and turning on without holding Shift.

Check Your Browser Settings and Extensions

Malware often changes your browser homepage, search engine, or adds unwanted extensions. Open Safari, Chrome, or Firefox — whichever you use most — and check the homepage setting. In Safari, go to Safari menu > Settings > General and look at the "Homepage" field. It should show a website you chose, not something unfamiliar.

Next, check your extensions. In Safari, go to Safari menu > Settings > Extensions. In Chrome, go to the three-dot menu > More Tools > Extensions. Look for extensions you do not remember installing. Legitimate extensions have clear names and come from known companies. Remove anything suspicious by clicking the trash or remove icon.

Also check your search engine setting. In Safari, go to Safari menu > Settings > Search and confirm it is set to Google, Bing, or your preferred engine — not something called "Search" or a random name. Malware often changes this to redirect your searches through ad networks.

Review Recently Installed Programs and Remove Suspicious Ones

Open Finder and click Applications in the sidebar. Look through the list of installed programs and note anything you do not remember installing. Legitimate programs have recognizable names — Microsoft Office, Adobe Creative Suite, Zoom, Slack. Suspicious programs might have generic names like "Installer", "Update", "System Tool", or random character strings.

To remove a suspicious program, right-click it and select Move to Trash. Some malware installs helper files in other locations, so removing the main program may not fully clean your system — this is why running a dedicated scan with Malwarebytes or Sophos is important. Those tools find and remove files scattered across your Mac that you cannot see in the Applications folder.

After removing programs, empty your Trash by right-clicking the Trash icon in the Dock and selecting Empty Trash.

Update macOS and Keep Your Software Current

Most Mac malware exploits security gaps in older versions of macOS. Keeping your system updated closes those gaps and prevents infection. Go to Apple menu > System Settings > General > Software Update. If an update is available, click Update Now and let your Mac restart when prompted. This usually takes 15 to 30 minutes.

Also update the programs you use regularly. In Safari, go to Safari menu > Settings > General and check "Keep extensions up to date". For other programs, check their individual settings or visit their websites to read the latest version. Outdated programs are another common entry point for malware.

Combining regular updates with caution about what you read — avoiding files from untrusted websites and being skeptical of unexpected read prompts — prevents most infections before they happen.

Frequently Asked Questions

Can Macs actually get viruses?

Yes, though the term "virus" is often used loosely. Macs are more commonly infected with malware — programs designed to show ads, redirect your browser, or steal data — rather than true viruses that replicate themselves. Macs are less targeted than Windows computers straightforward because fewer exist, but the infections that do occur are real and worth removing.

Is my Mac at risk if I only read from the App Store?

The App Store is safer than downloading from random websites because Apple reviews programs before listing them. However, malware has occasionally slipped through. Downloading from the App Store significantly reduces your risk but does not eliminate it entirely. Staying updated and running occasional scans is still worthwhile.

What should I do if I find malware?

Use Malwarebytes or Sophos to remove it, then change your passwords for important accounts like email and banking. If malware was present for weeks or months, consider monitoring your accounts for suspicious activity. Most Mac malware is designed for advertising rather than theft, but it is better to be cautious.

Do I need antivirus software on my Mac?

macOS includes built-in protections called XProtect and Gatekeeper that catch most common threats. Running a free scan with Malwarebytes or Sophos a few times per year is usually sufficient for most users. Paid antivirus software offers continuous monitoring but is not necessary unless you read files frequently from untrusted sources.

Why is my Mac slow even after I removed malware?

Slowdowns can persist if malware damaged system files or if your hard drive is nearly full. Check your storage by going to Apple menu > About This Mac > Storage. If you are using more than 85 percent of your drive, delete large files or programs you no longer need. If storage is fine, restart your Mac and run Activity Monitor again to see whether unfamiliar programs are still running.