If you notice that your Mac is slower than usual, or isn’t behaving the way it normally does, it may be due to malware…a word that includes viruses, worms, trojans, phishing scripts, and adware…all different kinds of files that negatively affect the performance of your computer.

Adware is a kind of malware that affects your web browsers. It may change your default search engine to a different one, or change your default home page. It may cause your browsers to slow down, or go to pages you didn’t expect.

Phishing scripts run in the background, without your knowledge, sending out thousands of legitimate-looking email message that appear to come from banks, auction sites like eBay or Amazon, payment processing companies like PayPal, social web sites, shipping companies, and web or email hosting companies. If you have one or more phishing scripts, one tipoff would be that you might be receiving a lot of email bounce messages showing that “your message” couldn’t be delivered to its recipient…except that you never emailed that recipient.

Viruses, trojans, and worms are the kinds of malware we’ve heard about for a very long time, that primarily affected earlier versions of Microsoft Windows…but there are some that affect MacOS as well. Fortunately for MacOS uses, they may cause the computer to behave slowly or cause intermittent glitches, but they are rarely more than inconveniences.

All of this malware can be removed, and we recommend using two different malware programs to do it.

  • Malwarebytes for Mac specializes in removing adware. It’s available in both free and paid versions, the difference being that the paid version is active in the background at all times. With the free version, you must run the program manually when you suspect adware. We recommend the free version unless you find you frequently are affected by adware. You can download Malwarebytes, which includes a 14 day free trial of their “paid” version, here. After 14 days, it reverts to the free version unless you purchase a license.


  • Antivirus software. Our favorite Mac antivirus is ClamXav. It costs $29.99 per year for up to 3 Macs, and that price includes all program updates and daily virus definitions updates. It runs in the background at all times and immediately quarantines any newly found malware. There are some free antivirus packages for Mac from Avira and AVG, but we find those pop up ads frequently asking you to upgrade to their paid versions. ClamXav is non-intrusive. You can download ClamXav here, and it includes a 30 day free trial, after which you must either buy a license or it will stop working.


Both Malwarebytes and ClamXav are easy to use. Once installed, Malwarebytes will open to the following window:

Malwarebytes For Mac Window

Just click the Scan Now button to scan your drive for adware and quarantine it.

The ClamXav window looks like this:

ClamXav will run in the background all the time looking through the files on your drive and quarantining malware files it finds. But if you can also scan manually by selecting what to scan in the left column, then clicking the Scan Now button. The Quick Scan looks for the most common kinds of viruses in the places they’re normally found. You can scan one or more specific files or folders by dragging them on top of the Drag Items Here icon. Or you can click on any disk current connected to your Mac and click the Scan Now button to thoroughly scan ever file on that disk.