Defender scans during the day when not scheduled to do so

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Guest

I have Windows Defender scheduled to scan overnight, but sometimes I don't
leave my PC powered up over night. In those cases, when I boot next day
Defender says "I should have run last night but didn't, so I'll run now".

I want an option to stop this because it spoils system performance.
(note: a full scan on my PC takes 1hr:15mns and scans 465,535 objects)
 
I would recommend that you change your scheduled scan to a quickscan. I
know this isn't a direct answer to the question, but Microsoft's
recommendation in product help is to run quickscans, and do a fullscan when
things are detected. I do full scans on "new" machines, but not routinely,
except to cover users storage on fileservers.

A quickscan looks at what is in memory, and the startup vectors, and works
outward from there--it is designed to catch in-place infections. And it is
far less resource intensive than a full scan--on office machines, I see
quickscans that take less than 2 minutes.

You can run a fullscan manually when you know you can spare the processor
cycles, or you could schedule a separate fullscan yourself, using the
scheduled tasks facility and mpcmdrun.exe.
 
Peter Facey said:
I have Windows Defender scheduled to scan overnight, but sometimes I don't
leave my PC powered up over night. In those cases, when I boot next day
Defender says "I should have run last night but didn't, so I'll run now".

I want an option to stop this because it spoils system performance.
(note: a full scan on my PC takes 1hr:15mns and scans 465,535 objects)
Click to expand...
 
I am annoyed that Microsoft has done absolutely nothing about this in two
months. If this defect isn't fixed I shall uninstall Defender and kiss it
good bye.
 
The scheduled scan is run by the Windows Scheduled Tasks facility. If that
is working correctly, scheduled scans should, as well.

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Bill Sanderson MVP said:
The scheduled scan is run by the Windows Scheduled Tasks facility. If that
is working correctly, scheduled scans should, as well.
Click to expand...
Well, that's not really my problem, it's Microsoft's. But I think the task
scheduler is working ok. What should happen is that when Defender is
activated as a scheduled task it should look at the time of day and see if it
corresponds to the time it is scheduled to run. If it doesn't, Defender
should not scan.

I expect that this problem arises like this: Defender is scheduled to run at
say 1AM. I use my PC upto 00:15AM and then power it down. Next afternoon I
power it up and Defender will start scanning.
 
You are correct about what is happening, and it is by design, as I
understand it.

(and the scheduler isn't doing this, the app itself is.)

The workaround I would recommend is to schedule quick scans--as the product
help recommends, and only run full scans either when something is found, or
periodically manually--or you can create your own scheduled job to do a
fullscan.

Full scans are quite resource intensive. Quick scans are much less so, and
are intelligently designed to try to catch anything which is actully
running, or set to run.


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