Windows 10: Windows Defender run time & number of files scanned

I have Windows 10, with all updates installed. When I run Windows Defender's Full Scan, it varies widely as to how long it takes to run and the number of files scanned. Today I ran a full scan and it finished in 21 minutes 214,812 files scanned. I thought this was not right, because it usually takes from 1-3 hours for a scan of my computer. So I immediately started another full scan just a couple minutes after the first scan ended. This one ran for 1 hr, 54 mins 920,547 files scanned. What's going on? Please give me a simple explanation if you know what's happening, as I'm not a "

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Reported number of files scanned differs, Defender window vs Notifications window

When I manually run a scan, Windows Defender will report 7720 files scanned (or some number in that vicinity). The Notifications/Actions Center will then present that there is a report "Windows Defender scan results" available to view.



Clicking that item opens the "Windows Defender Security Center" window which reports 5256 files scanned (or some number in that vicinity). The difference between these two numbers is seldom the same, but is always around 2464.

I have run consecutive scans 18 times this morning, getting numbers from 7774 to 7720 reported in the "Windows Defender Antivirus" window, and 5296 to 5256 in the "Windows Defender scan results" window. Differences in the count ranged from 2483 to 2464.

I can understand the variation in the file count from one pass to the next because of background processes (e-mail clients, auto-update actions, etc.) altering the number of files present, but why do the two reporting screens show such a large difference
in the count of files scanned per each scan?

 

How do I get Windows Defender to run a daily scan?

Hi Bill,

To run the Windows Defender automatically, we suggest that you follow the steps on this link:

Schedule a scan in Windows Defender.

Regards.

 

Defender not Running Regular Scan


I've never understood the need some people feel to set up a scheduled task to run a Defender scan. For the past year the automatic maintenance has run Defender scans for me.

That is, until the Anniversary Upgrade - it broke something and Defender never ran another scan. It finally alerted me that a scan was long overdue. I followed the suggestion on another thread...
Windows Defender No Longer Performs AutoScan
...and the automatic maintenance scans are back to running regularly again.