Question Windows 10 quick scan only 43 files and last 5 seconds all of a sudden

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Sep 18, 2019
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Maybe this is an optimization. It'd be nice. Makes sense, too, if I file hasn't changed, why bother scanning it. Sort of like incremental file system backups. I don't know if this is a valid optimization when it comes to security protocols?
Yeah, I'm inclined to agree with you and what the others alluded to earlier. Well, I'm just hoping that's what it really is rather than something sinister.
 

Ralston18

Titan
Moderator
Are you running the latest updates? I am getting truncated Quick Scans with the latest 9/10/2019 Quality updates (cum Win10, cum .NET, and security Adobe Flash) and 9/18/2019 Definition updates for Defender.

Microsoft Windows [Version 10.0.18362.356] on both Home and Pro. Your link is interesting, but I don't think it applies to either of my systems. I'm not running Enterprise.

Yes: Up to date with Windows 10 Pro 18362.356

I have another system that has not been used for a few days and has been turned off in the meantime. I am planning to boot it up, immediately block updates, and look at the current settings. Will run a quick scan.

Then allow any pending updates to install. Then watch what happens with the next quick scan.

As for the link - I did not read it as being only for Enterprise. That would be my error then.

On the other hand I have had occasion to discover that MS documentation is not always in sync with the bigger picture. One way or another.....

I find myself very much in agreement with @britechguy's comments.
 

britechguy

Commendable
Jul 2, 2019
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As an aside, but to reinforce the point made by @Ralston18, there is no software update synopsis that is, or ever was, intended to be comprehensive in describing what's changed. Having worked in custom systems development for many years, most of what changed would have been of no interest or concern to the end user. Many tiny fixes, tweaks, and improvements get made that are rolled out under updates where "the high points" in the release documentation do not discuss them at all. This is not limited to any single operating system or application, either. It's also one of the reasons I have repeatedly quoted this:

There really isn't a point to checking for updates and not installing them. . . It's important to install all available updates. I've been doing this since the days of DOS, and I still don't have the confidence to pick and choose among updates. There are just too many variables involved - and most people can't evaluate the full consequences of installing/not installing updates.

~ John Carrona, AKA usasma on BleepingComputer.com, http://www.carrona.org/

It is impossible for the average user, or even members of the development teams for different subsystems of an OS, to evaluate the full consequences of installing/not installing updates because full information is never provided. We don't expect our mechanics to go through every gory detail of what they did to make a repair or our lawyers to explain each and every last bit of a contract (particularly the "boilerplate" parts). We hire these people for their expertise and trust their judgment and expect they will give us the information we need, not every last detail. The same is (or should be) generally true of those responsible for maintaining the software we use. They will always know better than we end users do about what does and does not need to be updated and the reasons for same. Some of those reasons would be utterly incomprehensible to the vast majority of those using said software.
 

britechguy

Commendable
Jul 2, 2019
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See: https://answers.microsoft.com/en-us/protect/forum/all/quick-scan-through-windows-security/a5cdf599-5a4c-49f9-96d3-4900033f6147?auth=1

As I said earlier, if there's something to be fixed, it will be fixed. There may not be, but Microsoft is aware of the issue.

I'm way more concerned about realtime scanning on download than any drive scanning after the fact. The only updates I've had applied over the last 2 days are Definition Updates, 3 of them, and 2 of those were yesterday, so I suspect it's something with the Definition Updates of this morning.

Only time will tell if this is a feature or a bug, and it certainly won't be weeks in resolving (or getting the word out).

P.S.: If this is of concern, and I'm not saying it shouldn't be, then be certain to submit feedback via the Feedback Hub. Microsoft does pay attention to sudden patterns in feedback coming in.
 
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britechguy

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Jul 2, 2019
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They try to correct a bug and created another... Very nice.
Not the first, and certainly won't be the last time.

Odd, though, that the KB number identified by Mr. Abrams was installed on my system on September 16th, and several scans were run subsequent to that, including the normal one last night. There's still more to be revealed.
 
not affecting only Win10, apparently, folks with WIn 8 and Windows 7 have seen it as well...

Seems to be blamed on a recent definition update...(still can't rule out them implementing a plan of scanning only changed files, but, now folks even reporting secondary drives being skipped in the full scan option?Interesting!)

(I had another small WIndows update containing only a scan definitions update even after this scenario, but, still only 23 files or so scanned...naturally)
 
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Ralston18

Titan
Moderator
And I just ran a Quick Scan on another computer that has been up and running during the last couple days.

Shown as "up to date".

Quick scan = 4 files in 3 seconds and that is it.

Probably just wait this one out until the proverbial smoke clears.....
 

britechguy

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Jul 2, 2019
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I intend to wait it out, but just based on what's been offered here I am really strongly suspecting it's something in the very latest Definition Update, which is probably the easiest thing to fix - far easier than the code of Windows Security.
 
Sep 18, 2019
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Has anyone else tried running a Custom scan on your C: drive? For me, on two systems, this does do a complete scan, >800,000 files, over 10 minutes, etc. Quick and Full scans do the 8 second thing. Custom does what I would normally expect a full drive scan to do. (Go to scan options, select custom, hit scan, then select c: as your folder).

I don't know if this is a workaround, or revealing another bug in that Custom scans perform differently than Full scans.

I was an embedded systems engineer for a long time. It isn't uncommon to solve one problem and introduce another. Sometimes it isn't even unexpected. It may be moving from a high exposure/severity defect to a low exposure/severity defect, while the root cause is being addressed. I can just wait this one out... not being a Windows or security expert, I don't really have a choice... except to just reboot my two Win boxes with linux.
 
Sep 18, 2019
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I just updated to the latest security definition and it appears to be back to normal; 20538 files scanned in a minute.

Well, I'm just laughing at myself now because I sort of overreacted... About a half hour after I noticed the issue and with Defender Offline not working after the first two attempts, I immediately changed my master password for Bitwarden and then proceeded to start changing the passwords associated with more sensitive data; email accounts, Paypal, eBay, etc... lol
 

ex_bubblehead

Champion
Moderator
Known issue (for several days now):
https://www.forbes.com/sites/daveywinder/2019/09/19/windows-10-security-warning-as-microsoft-confirms-update-breaks-windows-defender/#5674afa65902


 
Sep 18, 2019
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bubblehead, that's been reported a few times now. I forgive you, 'cause I served too. On Nevada, SSBN733. Submarines&Targets... my captain was like that. He thought we were on a freakin attack sub. We ran targets all the time. XX knots, surfaced, at night!
 

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