Should one refrain from using the computer while a virus scan is in progress? Are there certain things that are ok and others not? For example is it ok to use a web browser while a scan is in progress?

This may be entirly unrelated but Avast 7 says "Multiple scans can be run at the same time".

  • In general, AntiVirus must set high priority to scan files when executed, if that feature is there, then, multiple instances of scan required and the performance will be decreased...
    – Akam
    Mar 30, 2013 at 8:34

4 Answers 4


Your AV might be unable to scan some files while they are in use. If that does happen, then any good AV should report this in a summary of the scan when it finishes, I'd have thought.

Performance could be pretty dire while it's running a scan, too!

  • Why would antivirus be unable to scan files while they are in use?
    – forest
    Aug 3, 2018 at 6:53
  • Unable is not the appropriate word. I believe they were referring to the AV might not have permissions to quarantine, remove or overwrite the file afterward (once the scan has completed) if the file is in use. Although, that statement changes from OS. e.g. Windows has Windows Explorer prevent deleting files which are in use.
    – safesploit
    Aug 3, 2018 at 10:14

For home users, perhaps the most reasonable practice lies somewhere in between the two answers already provided.

  1. Provide day-to-day protection by using the real-time activity monitoring functions of your antivirus product.

  2. Supplement this with scheduled weekly full system scans, preferably during off hours.

    • Overall system performance will likely be degraded for the duration of the scan, which could be an hour or more depending on how much data you have.
    • Scanning while the system is being operated could cause the scanner to miss some files which are in use. Your antivirus should log missed files.
    • Even during off hours, the scanner may miss some system files which are in use. Again, this should be logged. This is the reason I recommend #3.
  3. Finally, add a reminder to yourself to run a full boot-time scan of the system on a monthly basis.

    • A reboot will be required for this.
    • The scan will probably take an hour or more, depending on how much data you have stored. The system will not be usable at all during this time.
    • Depending on the response options you've set for the scan, it may halt for user input when a threat is detected. If you've left the scan unattended, this could further delay system availability the next time you want to use it. I suggest checking in on the scan from time to time, or some time before you actually expect to need the system again.

I suggest you make at least one full scan every week or two or even have one full scan once a month and a quick scan once a week after that. For the full scans, make sure it is the ONLY thing running and let it sit overnight until it has fully completed. For the quick scans, just wait them out they're never that long, you can do other things during these but, it's best if you let them be the only CPU usage this way they can work to their full potential. Also, restart your computer before you start the scan and completely exit any other program that starts up that is not necessary for your computer or your program you'll be using for the scan. Of course, restart after the scan and enjoy.

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    – Eric G
    Mar 30, 2013 at 4:59

Not preferred practice.

I would suggest to schedule boot-time scans {available in Avast too}, those are more effective for the viruses.

They take a time respective to number+size of files on your machine, but seem much more reliable to me.

  • 1
    This doesn't answer the question. It reads as "will I cause problems if I use the PC while scanning" whereas your answer seems to be for the question "when is the best time to scan"
    – Rory Alsop
    Jul 6, 2012 at 11:44
  • hope now it eases to understand the inference
    – AbhishekKr
    Jul 6, 2012 at 11:55
  • All you added to your post is "Not preferred practice." but I would argue that actually having a malicious file in memory means there is a better chance of it being caught.
    – Ramhound
    Jul 6, 2012 at 12:03
  • A boot-time scan is horrendously inconvenient to the user, unless they reboot the computer at the end of the day for it, or schedule the machine to turn back on an hour or so prior to the next expected use.
    – Iszi
    Jul 6, 2012 at 12:39
  • 1
    @Ramhound that was the only missing peice 'inference'; and if its in memory means its getting loaded from somewhere... but scanning in an already infected environment isn't that effective as the node involved in scanning is already infected.
    – AbhishekKr
    Jul 6, 2012 at 12:49

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