Why you don’t need to run manual antivirus scans (and when to do it)

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Do you regularly open your antivirus program and run scans? Some antivirus programs think you should do it and warn you that your computer may be at risk if you haven’t done it for a while.

In reality, these manual scans are not as good as they seem. You can usually ignore your antivirus and it will do its job in the background without your help, just letting you know when it finds a problem.

Why manual antivirus scans are unnecessary

Your antivirus always runs in the background. It is monitoring the processes running on your system, making sure no malicious processes are running. Every time you download a new file or open a program, your antivirus quickly steps in, scanning the file for viruses before allowing it to run. If you download a virus, your antivirus will notice it without scanning anything. For example, try downloading the EICAR test file – your antivirus will kick in and deal with the file without the need for manual scanning.

This feature is generally known as background scan, real-time protection, resident protection, on-demand scan, or something like that.

In other words, you don’t need to run manual scans because your antivirus has already checked each file for malware as it arrives. It is also aware of all the software running on your system. Your antivirus program doesn’t need you to click a button, it’s already doing the work.

The main Windows Security window.

When you should run manual scans

Manual scans are still useful in some cases, but you don’t need to regularly open your antivirus program and start them:

  • When you install an antivirus: When you install an antivirus for the first time, it will perform a full system scan immediately. This allows the antivirus to make sure that your computer is in a clean state and that you don’t have viruses lurking in unopened files on your hard drive. After performing this scan, your antivirus can be confident that your system is safe. However, it will still scan the files for malware when you open them.
  • Check for latent and missing malware sooner: Antiviruses use “definition files”, which are updated periodically. These files basically contain a catalog of identified malware, and your antivirus compares the programs you run against the catalog to see if they match. There may be a dormant virus lurking in an executable file deep on your hard drive that your antivirus missed during your first manual scan. If a virus definition has been added for that type of malware, or if the antivirus heuristics have been improved, it will only detect the dormant virus when performing a manual scan. However, the virus will be detected if you try to run the file containing the virus or during a regularly scheduled full system scan.
  • Get a second opinionNote: You should only have one antivirus program running at a time, as multiple background scanning antivirus programs can interfere with each other and cause problems with your computer. If you want to scan your computer with multiple antivirus programs, you will need to do a manual scan with the second antivirus program instead of using its background scanning feature.

Windows Security by running a manual quick scan.

Why background protection is better than manual scans

You can optionally disable background scanning in some antivirus programs and just perform manual scans, but you shouldn’t.

Think of your computer as your home, and your antivirus background scanning protection as a security guard standing at your front door and searching everyone who tries to enter your home. A manual scan is the equivalent of the security guard searching every inch of your home for intruders.

If you have already checked everyone who enters your house, you do not need to search every nook and cranny of your house for malicious people. In fact, it’s much better to secure your door because that way you can catch threats before they’re even allowed in; If you catch someone lurking in a dark corner of your home or PC, who knows what they’ve been up to in the time between when they were allowed in and when you caught them. Once the software is running on your computer, it also has the potential to hide itself and prevent your antivirus program, and even Windows Task Manager, from seeing that it is running. The software that does this is generally known as a rootkit.

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You want to catch malware before the virus starts running (and infecting) your computer, so stick with automatic background scanning instead of manual scans. Even if you scan all programs you download manually before running them, you should still use automatic scans for maximum protection against zero-day attacks and other security threats.

Windows Security has real-time protection enabled by default.

Some security suites may remove cookies when you perform a manual scan, referring to them as “threats.” This is a great way for the security suite to pretend it’s doing something valuable and justify its price. But you don’t need a full security package, anyway, and you can always have your browser automatically delete cookies if you want to get rid of them.

Of course, a lot of this depends on the antivirus software you use. Some antivirus software allows you extremely granular control over how your antivirus software works. Microsoft Defender Antivirus is generally pretty good, but it lacks some of the bells and whistles, and customization options, of third-party antivirus software.