I just checked mine and it scanned 12 files and that was it. I tried to roll the update back per the instructions on Microsoft’s page but it didn’t work.

I assume they will have a fix out soon.

We just ran into an issue just like this on Win 10, 1809 Edu. Stopped after a double digit count.

The machine was acting very weird- couldn’t run procexp, and taskmgr would quit on its own after about 15 seconds.

Quick and Full scan are broken, but Custom scan (e.g. selecting C:\) seems to work properly.

Noticed this, this morning. (W10 1903). Scanned about 29 files then exited. Thought no more about it as I needed to get on with things. Since I’ve got updates disabled I never thought (or had notice of) a silent update.

Thanks for the explanation!

I have just been running the following commands in a batch file when finishing work on a Windows 10 PC

sfc /scannow
First time this finds corrupt files but is unable to repair all of them

Then I run the next three to check the component store, check if repairable, then do the repair.

DISM /Online /Cleanup-Image /CheckHealth
DISM /Online /Cleanup-Image /ScanHealth
DISM /Online /Cleanup-Image /RestoreHealth

Not sure if the first two commands are absolutely necessary but it doesn’t hurt.

sfc /scannow
I run sfc a second time and now it is able to repair the corrupt files. Now we have another bad patch to contend with. It would have been better that they left well-enough alone. Windows Defender is far to important to screw up.

Its was not the engine update that caused this, as things worked normal after that, its only after the last few definition updates this started happening

Win 8.1×64.  Same as #1956105  Quick & Full Scans broken.   Custom seem to work o.k.

There is a workaround I’ve outlined within my English article now – it might work for Defender in WIndows 8.1, and it works for Windows 10 – and also for MSE in Windows 7 SP 1. HTH:

Scan issues with MSD/Defender Antimalware version 4.18.1908.7

W7x64 MSE , custom works  on mine but it’s the full scan so I use the quick scan ADWcleaner.

Microsoft Release Definitions Change Update Log
https://www.microsoft.com/en-us/wdsi/definitions/antimalware-definition-release-notes

Add me to the list. Quick Scan did 8 files in 9 seconds. Full stop. I have Win 10 1809 with up-to-date “forced” updates on an unexceptional but very functional HP desktop.

Surely Microsoft ought to be able to do better than that. I thought that MS had programmers and system analysts who are supposed to be the experts in those well-paid positions.

This discussion is about the failed function of scanning, which is important. But the first function of Defender for Win8/10 and MSE for Win7 is the real time protection of new files received. I think it is a good indication that the Custom Scan operates correctly. And so I hope the bug has not affected the handling of incoming data. Reaching definite conclusions is difficult. But I would be interested to read anyone’s best guess.

Also broken on Windows 8.1

Microsoft has released another definition update (1.301.1668.0) but doesn’t seem to solve the issue.

gborn wrote:

There is a workaround I’ve outlined within my English article now – it might work for Defender in WIndows 8.1, and it works for Windows 10 – and also for MSE in Windows 7 SP 1. HTH:

Scan issues with MSD/Defender Antimalware version 4.18.1908.7

After downloading todays latest MSE (or whatever it’s called now) definitions, scanning issue was present.
Did the work around (checking custom scan) and it worked.
Full scan of C drive successful.
Windows 7 Home Premium 64 bit SP 1

Thanks gborn!

Edit to add: current MSE info

b wrote:

Quick and Full scan are broken, but Custom scan (e.g. selecting C:\) seems to work properly.

I see the same thing

Will Microsoft ever do anything right?

anonymous wrote:

Its was not the engine update that caused this, as things worked normal after that, its only after the last few definition updates this started happening

I agree. The scan worked after the update to 4.18.1908.7.

After having a Quick Scan checking only 28 files earlier, I’ve just run an update and scan with MSE on one of my Windows 7 x64 machines, and it updated to 1.301.1684.0 then did a proper Quick Scan as usual, 16,478 files.

Could there be some clarification?

Were definition files causing this error or associated software within the definition files causing the error?

Things looked bundled to me and where’s the silent update?

? says:

feelings are hurt because Microsoft tips off Catalin Cimpanu and not Woody. anyway it wasn’t my run-a-way imagination when the MSE quick scan failed last Sunday. glad protection is back to “normal.”

F A Kramer wrote:

Add me to the list. Quick Scan did 8 files in 9 seconds. Full stop. I have Win 10 1809 with up-to-date “forced” updates on an unexceptional but very functional HP desktop.

Surely Microsoft ought to be able to do better than that. I thought that MS had programmers and system analysts who are supposed to be the experts in those well-paid positions.

Microsoft doesn’t have a QA department anymore and relies on insiders / home users for tests, but defender updates are not tested by insiders.

I could reply with thoughts about Windows Defender, yet doing so would turn into a rant. I will simply say that I gave up on Windows Defender long ago. Looking at some of the posts in this thread, it would appear that Windows Defender has been completely broken. I anticipate that hackers will figure out how Microsoft themselves broke Windows Defender. I consider this to be a security breach which was created by Microsoft, since the files needed to recreate this scenario are within Windows Updates. Say what you will in response, yet I will not reply.

Works on Win7-10

System File Checker (SFC) incorrectly flags Windows Defender PowerShell module files as corrupted (Last Updated: Aug 16, 2019)

To repair the Windows image files on computers that have been affected by this issue, use the DISM tool. To do this, open a Command Prompt window on the affected computer, and run the following commands:

dism /online /cleanup-image /restorehealth
sfc /scannow

Just checked and is fixed now.

Just updated to 18th Sept signatures and quick scan ok again.

FWIW, I usually have Defender on manual or disabled until I want to run it on occasion. I haven’t in awhile, but decided to now just to see what happened. Updated definitions to v1.301.1727.0 for 2019-09-19 and ran a quick scan.

Although it has been awhile, I always loved how fast the scans were which took almost no time at all to scan tens of thousands of files. I ran it just now and it took 5:19 to scan 52,017 files which seems a lot longer than it used to take before. It still ran smoothly and found nothing as usual, but does seem to be slower than it used to be.

I have MSE installed on 3 out of 4 of my Windows 7 laptops but those 3 laptops only get pulled out once a month to get only the Windows 7 Security Only updates with the 4th/newest laptop(Daily Use) that I own running Norton Security Suite(My ISP provider’s variant of Norton).

So I’m relatively unscathed from any July 2019 Security Only patches/issues because they have Telemetry and I skipped July on all my laptops. I did install August’s Security Only updates to all 4 of my laptops as there was no telemetry but because the 3 laptops running MSE are only taken out to be updated once per month they only get the MSE Virus Signature/Other update for the one day each month when they are taken out of the closet to get the monthly patching.

Now that SFC /scannow, on one of my laptops only and longer than a year ago, it was not able to fix some detected errors on one my older laptops but the SFC /scannow issue  what date was that first discovered? I do know the month in which MS intended to patch the SFC /scannow issue because that patch is what caused the Defender/MSE virus scans issue.

I will not be installing September’s “Security Only” Patches for obvious reasons so hopefully MSE will not have any virus scan issues by the time October’s MSE virus/other definition update is out/available. One other question remains with regards to MSE’s/Defender’s scanning engine updates that are pushed out with the virus definition updates is are they cumulative for any MSE scanning engine functionality?

With Windows 7 so close to going EOL I’m more than likely going to be Installing a Linux OS distro on the 2 oldest laptops and maybe 8.1 on the two laptops that are newest that are both running Quad Core Intel i7 mobile CPUs(One Sandy Bridge and one Ivy Bridge generation Quad Core i7 mobile CPUs). So that means all the laptops are getting re-imaged anyways with the Ivy Bridge laptop actually shipping with a Windows 8/8.1 Pro license but shipped by the OEM pre-downgraded to Windows 7 Pro via Pro OS version downgrade rights.

I’m also getting ready to Purchase some SATA based SSDs to replace the spinning Rust on 2 out of 4 of the laptops with the SSD getting Windows 8/8.1 installed from a fresh image.  So all 4 of my laptops are getting moved from Windows 7 over the next 6 months and I’m really not wanting to bother fixing any issues for Windows 7 when it’s so close to being EOL and the laptops getting re-imaged anyways with the Linux or Windows 8/8.1 fresh installs.

I sure hope that Microsoft does a final convenience roll-up for Windows 7 for folks that want to do a fresh install with all the KBs included and folks maybe only using those PCs/Laptops offline anyways after 2020. I  also be looking at purchasing a Windows 8.1 license key for the one laptop that’s getting 8.1 that did not ship from the OEM  with an 8/8.1 license. There are millions of folks running Windows 7 Pro Business Laptops, via Pro OS version Downgrade Rights, with those Laptops actually Licensed for 8/8.1 Pro.