How to scan your Mac for viruses

by Ross McKillop on January 12, 2009

Mac Security

According to the ClamXav home page -

Today, the number of viruses actively attacking OS X users is…NONE! However, this doesn’t mean we should get complacent about checking incoming email attachments or web downloads, for two reasons. Firstly, there’s no guarantee that we Mac users will continue to enjoy the status quo, but more importantly, the majority of the computing world use machines running MS Windows, for which an enormous quantity of viruses exist, so we must be vigilant in checking the files we pass on to our friends and colleagues.

So – do you even need anti-virus software on your Mac? That’s up to you to decide. If you do decide you want anti-virus software on your Mac, this tutorial will guide you through installing and using ClamXav – a free (and frequently updated) virus scanner for OS X.

  1. Start out by downloading ClamXav. Once the download has completed, open the DMG file, and drag ClamXav to your Applications folder.

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  3. ClamXav isn’t very large, so it won’t take long to copy/install.

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  5. Open up an instance of Finder. Select your user name from the left navigation window, and go to Library -> Contextual Menu Items. Back in the opened DMG window, drag ScanWithClamXav.plugin to the Contextual Menu Items folder. Sign out of your Mac (or restart, but signing out and back in will do the trick). Signing out and back in again will activate the “Scan with ClamXav” plugin.

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  7. Now launch ClamXav from your Applications folder. You’ll be prompted to install the Clam Anti-Virus engine. Click the Install button.
  8. On the Introduction screen, click Continue.

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  10. Review the Software License Agreement and once again, click Continue.

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  12. Click Agree to accept it, again.

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  14. Now click Install.

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  16. Enter your password when prompted, and click OK.

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  18. And now the scanning engine will install.

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  20. Click Close once the process has completed.

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  22. Now launch ClamXav from your Applications, again. Before you start the scan, click the Update virus definitions button.
  23. Once completed, you should see a Virus definitions updated successfully status message.
  24. Now click the Preferences button.
  25. On the General tab, make the selections that are appropriate for you. I opted to quarantine infected files rather than outright delete them, in case of any false positives (ClamXav flagging a file as being infected with a virus, when it in fact isn’t).

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  27. Depending on which settings you opt for, you may receive a message telling you not to turn on certain features if you plan on having your email scanned or watched. This wasn’t an issue for me as I use Gmail (via the web) but it is something to consider if you use Mail or Entourage for email.
  28. Select the Internet tab, and again, make any changes you see fit. I opted to have ClamXav check for all possible updates each time it starts.

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  30. Select the Schedule tab, and if you’d like to schedule virus scans, this is the place to create them.

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  32. Select the Folder Sentry tab. From here you can add folders to be constantly monitored for viruses (eg. your Downloads folder). Review the other options and make any changes you see fit. Click OK when you’re done.

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  34. Back in the main ClamXav window, click the Choose what to scan… button.

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  36. If you attempt to select your entire startup disk (as indicated in the screenshot below)…

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  38. you’ll get an error.
  39. So instead, just select all of the folders (hold down the Apple Key to select multiple items) on the drive you want to scan. Then click Open.

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  41. Finally, click the Start Scan button.

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  43. ClamXav will do a “quick” (it’s not that fast) scan of your drive to determine how many files it’s going to check.

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  45. And then they actual scan will begin.

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  47. At this point, you might as well settle in for the long haul. Depending on the size of your hard drive, the number of files on it, and the speed of your Mac, the process can take quite a long time. As indicated in the screenshot below, it took ClamXav 172 min and 31 seconds to complete on my MacBook Pro (an older one). With all of that said, I was able to work on my Mac the entire time without much of a noticeable slowdown. However, I kept my tasks to the relatively ‘safe’ – the last thing I wanted was a crash in the middle of the scan, forcing me to start over again. Running the scan overnight while you’re sleeping is probably a good idea.

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  49. And that’s it. Now you may want to scan your Mac for spyware, malware and tracking cookies.
  • http://insomnic.wordpress.com Insomnic

    I often recommend people get ClamXav on their Macs to scan questionable files (even if they won’t infect themselves they may pass it on). I also have it installed as a ‘safe’ place to scan those questionable files before moving them to my VirtualPC or onto other Windows computers at home or work.

    Thanks for posting the tutorial – so many Mac fans use the “no virus” argument that they won’t do an article about antivirus software.

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  • kris

    Hi! Thanks for creating this tutorial – it’s great! and I also used your MacScan tutorial and am waiting for the scan to finish. :)

    One question: My Mac doesn’t seem to have a “contextual menu items” folder (for the plugin) – I looked in Kris/Library/ and there’s no contextual menu items folder there. I also did a Spotlight search.

    Should I create this folder?

    Thanks!

  • Bullie

    Hi, I’m trying to download ClamXav on the link provided above http://www.clamxav.com/index.php?page=dl#TigerLeopard
    but receive an error msg said “The page you asked for does not exist on our server”. What have I done wrong here? I’m trying to download ClamXav for Leopard.
    Thanks for your help.

  • http://www.simplehelp.net Ross McKillop

    Bullie -

    I just clicked that same link you pasted in to the comment and it works perfectly for me (??). Try just going to http://www.clamxav.com/ and navigate to the downloads page, then find the version for Leopard.

    Cheers,

    Ross

  • Jerry

    Same here! No “contextual menu items” folder…

  • AJay

    I’ve been trying to follow the above steps but can’t get past step 4. I click Install and nothing happens. What’s up?

    AJB

  • WHOOO

    THIS WEBSITE IS AWESOME

  • http://facebook.com/Frankie91493 Courtney

    Thank you so much! It seems that I and many of my friends have become victims of a facebook virus, which dowloads to our computers and infects our aim accounts. I am sooo greatful you posted this, it was very useful! Thanks a million!

  • Michelle

    I installed the ClamXav but I am stuck on the third step-Contextual Menu Items. I could not locate that in my library. Please Help!!!

  • lauri

    just check to download and there is no version for 10.6 snow leopard ! now what

  • Deborah

    Bonjour,
    mon XamClav a détecté des fichiers avec virus, il les a mis en quarantaine. Mais que faire maintenant de ces fichiers et éliminer le virus?
    Merci.

  • Jessica

    I’m having some problems. I downloaded ok, then when I click the icon in my applications folder, it pops up then disappears. I can’t get past step 4. I did everything you said and I can’t get it to open. Please help!! I think I may have gotten a virus or something from facebook. Thank you!!

  • Maria

    for those stuck at contextual menu items dont go under devices and then to macintosh hd and go to library under that. the one under home doesnt have it

  • Maria

    *DO go under devices

  • Mike

    what should you do if ClamXav does find a virus? Does moving it to the Trash, then deleting solve the issue? or is there a more comprehensive way to delete that file?