Antivirus Slowing Your PC Down? Maybe You Should Use Exclusions

Retro Virus

Protecting your computer with an antivirus solution is par for the course when you’re dealing with a Windows PC, but unfortunately it slows you down at the same time. Here’s how to improve your performance, at least a little bit.

We’re not going to sit here and tell you to go without antivirus, since that would be irresponsible. What we’re going to do today is explain how you can exclude certain folders with write-heavy operations to speed up your PC without putting yourself into extra danger.

Note: Before you start excluding any files, you keep in mind that changing any of the default security settings could be risky, and you should probably close the browser tab and run away. Or maybe print off the article and burn it.  Also, the image is by xkcd

What Files Should You Exclude?

The general idea is that if you have some applications that are writing to the hard drive constantly, you should probably exclude the folders they are writing or reading from, as long as those applications are trusted and safe.

For example, if you’re using a virtual machine, which does both reads and writes from the hard drive on a fairly constant basis, you should make sure your antivirus application is not scanning those files and folders. Here’s a few examples of some things you may consider excluding:

  • Virtual Machine Directories: If you’re using VMware or VirtualBox, you should make sure those locations are excluded. This is actually what prompted this article, and probably the only significant performance boost out of the things we’re mentioning.
  • Subversion / TortoiseSVN Folders: Have you ever tried to do a big checkout of a source control project and had it fail? There’s a good chance that it’s conflicting with your antivirus application. This one has personally happened to me.
  • Personal Photo/Video Folders: Got you have a massive library of photos or videos that you’ve taken with your digital camera? As long as you only use this location for files copied from your SD card, there’s no reason to be scanning it and slowing your PC down while doing photo editing.
  • Legitimate Music Folders: If you’re downloading music from shady sources, this does not apply. If you’ve ripped your own CDs or downloaded from somewhere legitimate like Amazon, then you can safely exclude your music folder.
  • Windows Update Folders: This actually comes straight out of a Microsoft KB article—you’ll notice that they don’t recommend it, because they can’t do that in case somebody writes a special virus for the purpose of suing them, but the same principle applies.

Other Scenarios

There’s a nearly infinite number of applications and scenarios for everybody’s PC, so it’s hard to say exactly what is going to work on your PC—but there’s a way you can figure it out for yourself using Process Monitor, the great tool from Sysinternals at Microsoft.

Just open up Process Monitor, and then “uncheck” all of the little icons on the right-hand side of the toolbar, leaving only the “Show File System Activity” one checked. At this point you’ll see loads and loads of items in the list, with every access to the file system.

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You can use this data to figure out which applications are constantly reading and writing to the hard drive, and then based on the safety of those files, you can choose whether or not to exclude them.

Don’t Exclude File Types, Exclude Folders

When you exclude a filename or file extension, you are telling your antivirus software to completely ignore those files anywhere on your system, which could cause a security problem. It’s a much better bet to exclude a particular folder that you know is safe, like your virtual machine folders.

Always Scan Files from the Internet

I’ll start by saying this should go without saying… which always seems to be said anyway… but you should make absolutely certain to scan any files that come from anywhere on the internet, and especially when those files come from torrents or other similar sources rife with viruses.

All Antivirus Applications Work Differently

The next thing to mention is that not every antivirus application is going to work the same way—for instance, by default, AVG only scans a specific set of file extensions, and files with no extensions. There’s no way to tell—without benchmarking, at least—whether excluding folders will make a performance difference if they don’t scan those extensions.

Some other anti-virus applications, however, don’t limit themselves to specific file types, so you’ll need to dig into the settings for your particular application.

Excluding Files from Microsoft Security Essentials

Microsoft Security Essentials makes it real simple to exclude files—just head into the Settings, choose Excluded files & locations on the left-hand side, and then add folders into the list on the right-hand side.

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You’ll probably notice that MSE doesn’t slow your system down very much anyway.

Excluding Files from AVG Anti-Virus

As we mentioned earlier, AVG works a little differently—if you head into Tools –> Advanced settings…

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Then head to Resident Shield –> Advanced Settings to see the list of file types that are currently being scanned. You’ll notice that AVG always scans files with no extensions, which shouldn’t normally pose a problem, but depending on the applications you’re using there might be a problem.

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You can switch to the Resident Shield –> Excluded Items to add in folders or specific files to exclude from scanning.

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We’re not going to cover every other antivirus application, but they all pretty much work the same. Also, we prefer Microsoft Security Essentials.

Funny Related Story

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About 10 years ago, when I was still fairly new at the vaporware company I was working for at the time, the ILOVEYOU worm attacked our email system, crushing our Microsoft Exchange server with an overload of emails, and then the worst possible thing happened—our email server became corrupted. The IT staff ran the recovery tools, which fixed the problem and all was well… for a few hours until it became corrupted again. And again.

After a couple days of this problem, I finally popped my head in the door and asked to take a look. Sure enough, the problem became very clear within minutes.

That’s right. You guessed it…

They had installed the desktop edition of Norton Antivirus on the email server, and they didn’t exclude the database folder for Exchange. Virus-laden emails came into the Exchange database, and then Norton proceeded to rip them right out of the database itself, corrupting the files badly in the process.

Of course, I removed Norton and proceeded to grab a reputable antivirus plugin for Microsoft Exchange, which cleaned the emails the proper way, and all was well. Until the brilliant IT person installed Norton again. *sigh*  At least I got a promotion out of it.

Wrapping Up: Use This Tip At Your Own Risk

Just to wrap up, and as we said earlier, forget that you read this article, and if you get a virus don’t blame us. This especially applies if you’re not really sure what you’re doing—this probably isn’t something you should mess with.

Lowell Heddings, better known online as the How-To Geek, spends all his free time bringing you fresh geekery on a daily basis. You can follow him on if you'd like.