Avast Free Mac Security Review: Our Top Free Pick

Avast Free Mac Security provides very good antivirus protection for free, and it throws in email scanning on top. Unfortunately, this software doesn't offer any other perks that you can't find elsewhere for free.   

Costs and What's Covered

Avast Free Mac Security is free. It supports Macs running any version of OS X, as long as they have 128MB of RAM and 750MB of available disk space.

MORE: Best Mac Antivirus Software

Antivirus Protection

Avast Free Mac Security keeps Macs free of malware using traditional signature-based detection and by unpacking Mac-specific formats and scanning them for malicious contents. It also detects and quarantines PC malware on Macs, to prevent it from spreading.

Not only does Avast monitor your computer and its network connections in the background, but it also allows for both on-demand and scheduled scans. Avast additionally scans your router to look for signs of malicious DNS hijacking and executable shellcode scripts. The program also scans unopened archive files such as ZIPs.

Antivirus Performance

Avast Free Mac Security's on-demand malware-scanning engine does a very good job of keeping a Mac infection-free. The engine stopped 99.17 percent of Mac OS X malware in German independent lab AV-TEST's most recent evaluations, conducted in June 2016. That's just below Bitdefender Antivirus for Mac's perfect, 100 percent score.

Avast tied with Kaspersky Internet Security for Mac, Sophos Home for Mac and Norton Security, which also all scored 99.17 percent, and did better than Avira Free Antivirus for Mac, which stopped 93.33 percent.

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Security and Privacy Features

Avast includes its Online Security browser extension, which automatically installs itself in Chrome unless you opt out, while Firefox provides a confirmation prompt to make sure you approve. The Avast extension appears as a button that is green when you're safe and red if a site is potentially harmful. Similar flags will appear next to search results.

If you're wary of sites that monitor your actions, Avast also displays a counter badge that tallies the number of activity trackers found in a website, and provides an additional option to block social network-based tracking.

Not only does Avast scan activity on your hard drive and web browsers, but it also monitors POP3 and IMAP email clients, including Apple Mail, Thunderbird, Postbox and Airmail.

Not only does Avast monitor your computer and its network connections in the background, but it also allows for both on-demand and scheduled scans.

However, Avast Free Mac Security doesn't have any of the extra features offered by paid competitors, such as firewalls or webcam blockers.

Performance and System Impact

Avast Free Mac Security had a moderate impact on system performance, which we assessed by running our custom OpenOffice benchmark test that matches 20,000 names and addresses on a spreadsheet. Our test machine was a Late 2013 MacBook Pro with Retina Display with a 2.6-GHz Intel Core i7 CPU, 8GB RAM and 23GB of data stored on a 512GB SSD.

With Avast Free Mac Security installed on our MacBook, but without any active scans running, the OpenOffice test finished in an average of 2 minutes and 23 seconds, one second longer than without any antivirus software installed. That's a passive system hit of 0.7 percent, not something you could likely perceive. Other antivirus products' passive system impacts ranged from 1.41 percent to zero percent.

In AV-Comparatives' tests, Avast detected 99.9 percent of malware.

You would be more likely to notice the slowdowns created by Avast's active scans. During full-system scans, the OpenOffice test finished in an average of 2 minutes and 37 seconds, a performance dip of 10.6 percent. That's not bad, although it wasn't as good as Kaspersky's 6.34-percent full-scan system hit. The worst performer in this test was Norton Security, which had a 28.17 percent system impact, something you would probably notice.

Avast's full-scan completion time was 17 minutes and 15 seconds, near the middle of the pack. By contrast, Bitdefender took only 31 seconds, winning the speed prize, while Sophos lagged behind, at 2 hours and 25 minutes.

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Avast's moderate system impact may be due to the fact that this program scans every file every time, unlike Bitdefender, which skipped unchanged files it had previously reviewed. The full-system scans of Kaspersky (which also scans every file every time) and Sophos took even longer to complete, but those longer times may have allowed the software to reduce system impacts.


Unlike other free antivirus software, Avast Free Mac Security provides a data-rich interface that gives users plenty of data and options. Its main window shows users a Protected status, as scans are enabled by default.

Avast's main window presents users with their status — Protected or otherwise — and a New Scan button. Clicking on New Scan presents a Start button for activating a Quick Scan and a Change Scan Type button to switch to a full-computer scan.

In the Scan tab, you can command Avast to search your whole system, mounted drives or discs, specific folders, or connected network devices. Avast representatives told us there is no scheduled scan option because the company believes you need only an initial hard-drive scan followed by background scanning.

You'll find database updates and analyses of scans performed on your system in Avast's Reports. Avast places files it flags as malicious into the Virus Chest quarantine section, where you can delete or restore them (if you think Avast is mistaken). Open the Shields section to see real-time analysis of scanned files.

In the Preferences tab, you'll find options to change the frequency of notifications, system updates and scans. Here, you can also disable hard-drive, email and web protection, though Avast makes you enter your system password first. Additionally, you can disable Avast's menu bar icon from this window.

Avast Free Mac Security had a passive system hit of just 0.5 percent on our MacBook, which is the second lowest rate we found.

If you create an account with Avast, you can check the status of any systems you've logged into in the Account tab, as well as at my.avast.com. Avast's menu bar button provides links to open the main interface window, see current activity and application information, and review previous notifications.

Installation and Support

To install Avast Free Mac Security, you open Avast.com and click Download. You'll be sent to Download.com, where you click the big, green Download Now button, which will place the installer DMG on your Mac. After you click through the end-user-license agreements, the installer will download more files and install Avast.

No restart is required, and the whole process took about two minutes for me, slightly less time than with some competitors. During that process, you'll be prompted to opt out of installing the Avast Online Security browser extension and the company's SecureLine VPN client. (You should also check to make sure no other software is set to be installed.) Avast Online Security is free, but you get only a seven-day trial of SecureLine VPN, which you can activate from a menu bar icon.

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To get technical support, click Help in the menu bar, select Avast Technical Support and select Contact Help to open Avast's Support site. Here, you can find a FAQ, ask for help in the forums and call a customer support line that will provide free support for installing, configuring, updating and removing Avast. If you need more help than that, Avast offers paid support that starts at $119.99 for one-off support calls, as well as yearly support plans for one year at $179.99 and for two years at $299.99.

Bottom Line

Avast's email scanning is a welcome bonus, and its malware-catching abilities are very good. But a lack of other security features and a noticeable dip in performance during a full scan makes it hard to recommend Avast Free Mac Security over the easier-to-use free Sophos or the more capable paid Bitdefender.

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  • Captain Yesterday
    For some Macs, the "Best Free Mac Antivirus" according to "Best Antivirus Software and Apps 2016" would be Avast, not Sophos. Specifically, those running OS X 10.7 and earlier, since August 2016 was the last time that the last compatible version (9.4.2) added a newly-downloaded virus definition (after having been reduced to limited support in November 2014 and zero support in November 2015). So I decided to try switching. So far it seems a perfectly serviceable replacement, though with fewer of Sophos' user interface features I enjoyed.

    During installation I unchecked "install browser plugins". One, I use Firefox which already includes a perfectly good Mozilla blocklist service, and I suspect filtering all web accesses through multiple blocklists exceeds the point of diminishing returns. Two, I don't use Mozilla's blocklists either because I use MVPS hosts and NoScript and have enough confidence to prefer keeping my network and system resources away from blocklisting. Three, if there was any adware (I have no idea), a browser extension is the most likely host. Four, complexity is the enemy of efficiency and reliability (see the KISS principle).

    Thanks to Little Snitch, the first thing I had to do after installation was Avast >> Preferences >> Shields >> Web Shield >> Disable. Because Web Shield renders Little Snitch a useless waste. Because Web Shield creates a virtual proxy network (to inspect all the machine's network connections) in between the applications and the physical network, and Little Snitch can only see the applications connected to the physical network, i.e, Avast-proxy. For anything to work, Little Snitch would have to be told to allow all Avast connections, exactly the same as having no Little Snitch at all. So, buh-bye Web Shield.

    I can't remark on Avast's Mail Shield because I do not use mail applications on my machine, I use exclusively email service providers' web interfaces (a.k.a. webmail). So, the second thing I did after installation was turn off Mail Shield (otherwise I'd leave it on).

    The third thing I did after installation was Avast >> Preferences >> Updates >> uncheck everything. In my decades of computing experience, unmanaged automatic updates were the Number One source of avoidable problems (see Windows 10). That makes the only reason to ever allow anything to update randomly is an inability or unwillingness to update deterministically. And that's one problem I never had.

    Thanks to Little Snitch, the fourth thing I did after installation was delete all Avast-related Little Snitch rules and start over, approving new rules for (manual) Update Virus Definitions, Update Program, Scan Network, and Help (except denying access to apis.google.com, code.jquery.com, connect.facebook.net, fonts.googleapis.com -- give me a break). I also denied all network access for com.avast.account-sync since I do not have an Avast account.

    So far, everything seems to work perfectly. I only have 8 issues so far, all only with the user interface.

    Issue #1: logging. Installation threw a whole mess of tiny log files in /private/tmp, but not a single one where the Console app can see them. If it's not written to the system log, it's gone (or possibly hidden). Why? Are any of those hidden log files useful, or persistent? Dunno. Will take a while to find out.

    Issue #2: opening Avast. It never remembers its previous window state, it always opens to Status. Why? What if I want it to open to Preferences >> Updates, why not? It's not AppleScriptable either.

    Issue #3: "Status". If 100% of Avast's automatic services are not enabled, it asserts "You are not protected" with a Big Red X. Why? I am 100% as protected as I wish. If that's not a "You are protected" Big Green Checkmark, it's at least a "You are partially protected" Big Yellow Triangle; quit lying. So there's no easy way to tell whether or not my specified protection level is fully operational. Why not?

    Issue #4: scans. It moves all suspect files to its Virus Chest without allowing any opportunity to confirm its suspicions first. Why? Alarmed at the prospect of unintended consequences of unwarranted filesystem modification, the first thing I did was immediately have them all moved back, but in doing so, Avast wrongly changed some of their modification dates. That's bad if you use modification dates to indicate, say, dates of modification. Automatic relocation of suspects should be optional, not forced.

    Issue #5: reports. Reports aren't functional. After restoring all the Virus-Chested items to their proper locations, the intent was to subsequently investigate each item individually at my convenience, and return it to the Virus Chest only if necessary. But items restored from the Virus Chest leave no trace...except in the Report, which is just dumb pixels with no way to act on or even copy the file path of an item. Why?

    Issue #6: reports. Reports aren't outputtable. There is no way to save a report. There is no Console-readable log of a report. There is no way to copy any text off a report to paste somewhere else. They are just dumb pixels, and all anyone can do is take a screenshot of them. Why?

    Issue #7: reports. Reports disappear easily and permanently. After a Full System Scan I experimented with the Home Network Security Scan 4 times, and suddenly my Full Scan Report was gone, never to be seen again. What? Why?

    Issue #8: manual updating. There is no convenient Update Now method using the menubar icon menu or anything else. There is exactly one manual update procedure: (1.) open Avast, (2.) click Preferences, (3.) click Updates, (4.) click Virus Definitions Update Now, (5.) type password, (6.) wait, (7.) click Program Update Now, (7.) type password again, (8.) wait, (9.) quit Avast. It doesn't even retain administrator privileges from one action to the next. Why? Is not automation kinda the thing computers were invented to do?

    Again, no issues I found interfere with protection from malware, only with user experience. Thus I am satisfied with switching from Sophos to Avast so far.