Computer Related > Widows defender antivirus slowing PC Miscellaneous
Thread Author: bathtub tom Replies: 42

 Widows defender antivirus slowing PC - bathtub tom
My PCs slowed somewhat recently and I think it's due to Windows antivirus. I closed my ISP and looked at task manager with nothing else running.
Antimalware Service Executable, Windows Defender Antivirus results are:
CPU 50%, Memory 125MB, Disc 40MB/s
I presume this is the cause of the problem. Any suggestions, should I ditch defender for some other protection or can I reload it to overcome some problem?

PC: AMD Athlon (tm) X2 250 processor 3.00 GHz, 4.00GB RAM
64 bit operating system, 64 based processor

Windows: 10 Pro, version 1803
 Widows defender antivirus slowing PC - smokie
I wouldn't ditch Defender as it is doing a grand job for me (so far) and probably for millions of others.

In itself, 50% CPU isn't serious, that's actually an underutilised CPU in some people's book.

More likely that the 40MB/s disk use was clobbering the disk and slowing the system, as the disk is used for other stuff too (memory swaps)

I expect Defender was doing a scheduled scan or suchlike - do you have it set to do that? If so it's best left alone while it completes it, as interrupting may cause it to start from the beginning each time. Maybe if you set it to do a deep scan manually and leave it top run it will complete and the scheduled one won't keep re-trying..
 Widows defender antivirus slowing PC - smokie
PS that's assuming you meant Windows Defender, not Widows Defender as per title :-)
 Widows defender antivirus slowing PC - bathtub tom
>>More likely that the 40MB/s disk use was clobbering the disk and slowing the system, as the disk is used for other stuff too (memory swaps)

I've been checking this over the past few days, in case it was an update. The 40MB/s disk use is consistent. In fact when the PC's idle you can hear the disc chattering away and see the front LED flashing. It's something that's occurred recently.

nnnnnnnnnnnnnnnn - yes that key works.
 Widows defender antivirus slowing PC - No FM2R
Interesting, recently I have found the same thing.

About the usage levels that you are seeing by the same Antimalware Service Executable.

*But* it's not consistent nor constant. Right this moment, for example, it's not doing anything untoward at all.

It is not related to a scheduled scan, though it may be related to some other kind of checking.

I've been puzzling over it for about 3 weeks. I'm of half an idea that it is related to Windows update in some way.

Perhaps it's checking files being download for updates. I'm not sure and I haven't really done much focussed on it. I was kind of waiting for something to twig, become detectable or obvious.

I wouldn't ditch Defender at this stage, if I were you. I'll let you know if I get anywhere with it.
 Widows defender antivirus slowing PC - bathtub tom
This is stupid, I'm down to dial-up speed of response. I feel I've no option other than to ditch defender for another antivirus.
"I'm stepping outside, I may be gone for some time"
 Widows defender antivirus slowing PC - smokie
What's it like for stuff which isn't using your connection?
 Widows defender antivirus slowing PC - rtj70
An older install of Windows 7 with Defender issues for some was similar for what BT is reporting.

For me this was a quad core 2.6GHz hyper-threaded system with 16GB RAM. Way too much resource being used. It was stuck rebuilding system files. I just disabled it and later rebuilt it as little on there matters to me.
 Widows defender antivirus slowing PC - bathtub tom
>>What's it like for stuff which isn't using your connection?

Closed my browser and turned off the router and it's still the same.
 Widows defender antivirus slowing PC - No FM2R
It's the disk usage that's killing you.

I'm looking at it now as it's just started happening again.
 Widows defender antivirus slowing PC - No FM2R
Searching for outstanding updates, then rebooting, seems to have made the problem go away.

I'm pretty sure that my issue lies in this area.


For you, do check the disk, a failing disk can suddenly start hunting all over the place. Various free disk checker tools are available.
 Widows defender antivirus slowing PC - smokie
Yeah i was mentioning disk use earlier. However if it's in the middle of a scan and you reboot it, it may well be OK until next time it does the scan. IMO it's best to leave it for many many hours and see if it completes. If not then start an investigation.

Might be worth clearing your internet cache as there may be something inadvertently downloaded which could be trying to block Defender running properly, or causing it other grief.

(Some recent Windows updates take many hours even on a well specc'd PC, and scanning and decompressing etc would all be stressful on the disk without much discernible outcome for many hours. Keep interrupting it and it will just keep restarting...)

Doing a disk check is also a good idea, nothing to lose.

Also I suppose worth checking that the disk isn't nearing being full, as that would cut down space available for swapfiles.
 Widows defender antivirus slowing PC - No FM2R
That's the thing; it is *not* doing a scan, but it is very active. Or at least, not a routine scan. It also seems that either "Windows Update" or "Update Orchestra Service" are active at the same time (ish)

I think it's checking downloaded files as part of that, though I am struggling to prove it to my own satisfaction.


EDIT: Right this moment, Windows Update, Update Orchestra Service and Antimalware executable taking 47% disk With "Windows Modules Installer Worker" popping up and down.
Last edited by: No FM2R on Wed 18 Jul 18 at 17:55
 Widows defender antivirus slowing PC - No FM2R
And it is

2018-07 Cumulative Update for Windows 10 Version 1803 for x64-based Systems (KB4345421)

driving it all.

See what happens when it finishes.
 Widows defender antivirus slowing PC - No FM2R
Right, here's what is happening to me....

Computer starts to get slow. Eventually I notice as it becomes unbearably slow. When I check, it seems to be Antimalware Executable that is utilising the disk to a ridiculous level. Occasionally Windows Update, Orchestra Update and Module installer are joining in.

There is no scan that I can see.

I open Windows Update and it says there are none outstanding. I force it to check for updates, despite it saying that it only checked yesterday.

The computer then grinds to a halt before eventually admitting that there is an update available and it will, if I'm nice, install it.

Then, after the update, everything is back to normal and functioning properly.

Until the next time.

p.s. and this is the third time I've been able to follow these steps. I have followed every Windows repair, update repair etc, etc, process you can think of, and it still recurs.
Last edited by: No FM2R on Wed 18 Jul 18 at 18:31
 Widows defender antivirus slowing PC - smokie
I believe Defender does scan newly downloaded files as a matter of course and doesn't wait for a scheduled scan. That could account for why you can't see a scan happening yet the task is active.

I wonder if doing the update in Safe mode would prevent Defender working, and allow the upgrade through more quickly? Of course you'd have needed to have downloaded the update before rebooting into Safe as you wouldn't really want to be online without Defender.

I think these Microsoft links will get you the package you are sticking on

64 bit download.windowsupdate.com/d/msdownload/update/software/updt/2018/07/windows10.0-kb4345421-x64_c5a035dc1ec030a5be0626c8b019b9c4f6e8a1a6.msu

32 bit
download.windowsupdate.com/c/msdownload/update/software/updt/2018/07/windows10.0-kb4345421-x86_74331e092aa326fc34f320ecc46e56d88017887b.msu

The 64 bit package is nearly 700mb so really would genuinely take some time to scan... and require a useful lump of spare disk space!! Especially as Windows tries to save the old version before upgrading to the new one.

(You can clear old versions of Windows through File Manager - right click on your disk, go to properties, general, disk cleanup, click Clean Up System Files and select which ones to clear - you'll see that sometimes there is a huge amount of data taken up by them!!)

You may even find that just downloading and then running these files would not go through the same process as the automated update and may work OK.

Till the next time :-)
 Widows defender antivirus slowing PC - No FM2R
It doesn't actually stick on any given package, it will install it when pushed to. But every time a new package is due this seems to be happening again. It seems to be happening in that gap between it deciding that there is an update there, starting to download it, but then not actually installing it until the computer is idle.


I wonder if I can simply exclude that directory from scans....?

It offered to clean up 5GB of files, but given that the system disk has currently got 1.54TB free I'm guessing that won't matter much.
 Widows defender antivirus slowing PC - smokie
Oo'er, just had a look at updates on my PC (this one) and I have a restart pending for the one hat is troubling you.

So I may be back soon, or maybe tomorrow :-)


EDIT: Went OK, I guess the update was already applied and the reboot was required just so it can replace files currently in use. So it seems I didn't get the same issues you are seeing...
Last edited by: smokie on Wed 18 Jul 18 at 20:42
 Widows defender antivirus slowing PC - bathtub tom
Checked updates in settings and have the following message:
'We can't install some updates because other updates are in progress. Restarting your computer may help, and we'll keep trying to update.'

I presume this is my problem.
Any suggestions as to how I get round it? It doesn't tell me which updates are causing the problem.
 Widows defender antivirus slowing PC - Zero
>> Any suggestions as to how I get round it? It doesn't tell me which updates
>> are causing the problem.

You could wait till those nice people from India notice because they have been checking your pc, and offer to help?

Or you could google "how to check what updates have installed"

which provides (among others)


www.tenforums.com/tutorials/5472-view-windows-update-history-windows-10-a.html
Last edited by: Zero on Fri 20 Jul 18 at 14:42
 Widows defender antivirus slowing PC - bathtub tom
Think I've found them:

"We can't install some updates because other updates are in progress. Restarting your computer may help, and we'll keep trying to update."

Update for windows antivirus antimalware platform KB4052623 (version 4.18.1806.18062)
Failed to install on ‎27/‎06/‎2018 - 0x80070643

Definition update for windows defender antivirus KB2267602 (definition 1.271.105.0)
Failed to install on ‎27/‎06/‎2018 - 0x8024000b

2018-07 cumulative update for windows 10 version 1803 for x64 based systems (KB4338819)
Failed to install on ‎11/‎07/‎2018 - 0x8007139f

I'd appreciate any help in resolving this please. Do I have to uninstall these failed updates, or can I just install them manually?
Last edited by: bathtub tom on Fri 20 Jul 18 at 14:48
 Widows defender antivirus slowing PC - No FM2R
When did you last reboot the computer? Recently?
 Widows defender antivirus slowing PC - No FM2R
And yes, this is almost certainly your problem.


If not rebooted recently, then reboot it now.

Also, try going to;

Control Panel / System & Security / Troubleshoot common computer problems / Windows Update / run the troubleshooter

It's more useful than you might think.
Last edited by: No FM2R on Fri 20 Jul 18 at 15:38
 Widows defender antivirus slowing PC - bathtub tom
It's just been re-booted a couple of hours ago as advised by the windows message - no change.
 Widows defender antivirus slowing PC - No FM2R
Try that troubleshooter. It's helped me in the past.


If that doesn't help, we can try downloading and installing the updates manually, but the troubleshooter is a good first step.
 Widows defender antivirus slowing PC - bathtub tom
I've run the troubleshooter and got the following message:

"Issues found
Potential Windows Update Database error detectedPotential Windows Update Database error detected
Possible issues may prevent Windows Update from keeping your system up to date. Detected Detected
Repair Windows Update Database Corruption Not run"

Does this mean there's still a potential problem?

I also got the following messages which were more promising:

"Windows Update components must be repairedWindows Update components must be repaired
One or more Windows Update components are configured incorrectly. Fixed Fixed
Repair Windows Update components Not run"

and

"Check for pending updatesCheck for pending updates Fixed Fixed
Download and install pending updates Completed"

It does seem to be running faster.
 Widows defender antivirus slowing PC - No FM2R
Look in Task Manager, how high is the disk activity and is Antimalware Executable still there and high?
 Widows defender antivirus slowing PC - No FM2R
If Tack Manager is normal and checking Windows Update shows no outstanding updates then it's probably ok.

Bear in mind that your PC may now be working through a backlog of updates.

If you think there is still an issue, then have a look at this;

troubleshooter.xyz/wiki/fix-windows-update-database-corruption-error/

I wouldn't bother with "Method 2 Clean Boot" it never seems to work.

It's a matter of working through that document, probably 3 or 4 will do the trick.

Let me know how you get on and whether or notou need any clarification or assistance.
 Widows defender antivirus slowing PC - rtj70
This problem sounds similar to what I had on Windows 7. It was busy trying to update it's own config. I just ditched defender back then because I rarely turn on the PC anyway.
 Widows defender antivirus slowing PC - bathtub tom
PC's certainly running faster and task manager shows defender disk use down to 1% or less, although it shows it using around 50% of CPU.

Tried No FM2R's link, but got a different menu to that shown when pressing windows + X and no command prompt option.

Many thanks to all who helped.
 Widows defender antivirus slowing PC - bathtub tom
Checking my update history, I still have a couple that have failed:

1. 2018-07 cumulative update for windows 10 version 1803 for x64 based systems (KB4338819)
Failed to install on ‎11/‎07/‎2018 - 0x8007139f
I've found this, downloaded it, but get the message it's not relevant to my PC.

2. 2018-07 cumulative update for windows 10 version 1803 for x64 based systems (KB4345421) (2)
Last failed install attempt on ‎22/‎07/‎2018 - 0x8007139f
I've found this, downloaded it, but get the message it's already installed.

Are they necessary?
 Widows defender antivirus slowing PC - rtj70
The second fixes things the first one may have broken on servers. Have you downloaded and tried running the standalone installers for these?
 Widows defender antivirus slowing PC - smokie
I just had a bit of a read about this and an obvious suggestion we've missed is to run a check disk and also open a cmd window as administrator and type sfc /scannow the press enter.

Both may take some time and will probably not help but an easy thing to try.
 Widows defender antivirus slowing PC - bathtub tom
>>I just had a bit of a read about this and an obvious suggestion we've missed is to run a check disk and also open a cmd window as administrator and type sfc /scannow the press enter.

Done a check disk (no problems found), but the second half of your reply is beyond my experience. I'll have to go and google that (after the F1 highlights).
 Widows defender antivirus slowing PC - No FM2R
>>Done a check disk (no problems found), but the second half of your reply is beyond my experience. I'll have to go and google that (after the F1 highlights).

Right click on the windows symbol in the bott0m left corner.
Left click on "Windows Powershell (Admin)
Click on "yes" to allow the shell to make changes

At the prompt type "sfc /scannow" and hit return

Wait, read any error messages or commentary, then exit.

But *only* do it if you suspect that you still have an issue, otherwise it's simply a waste of time.

 Widows defender antivirus slowing PC - bathtub tom
>> The second fixes things the first one may have broken on servers. Have you downloaded
>> and tried running the standalone installers for these?

Done that.
 Widows defender antivirus slowing PC - Stuartli
The KB4345421 Update didn't install on the first attempt in my case, but did the following day (I check manually for Updates, rather than let Windows do so and install automatically).

A list of updates up to the current date can be found at:

tinyurl.com/y85q8u5y
 Widows defender antivirus slowing PC - No FM2R
>>I check manually for Updates, rather than let Windows do so and install automatically

Why?
 Widows defender antivirus slowing PC - Stuartli
>>Why?>>

For the very simple reason that Windows Update can state it did a check even a few minutes ago and it's up to date, yet if I Check for Updates manually quite often a new or new ones will become available.

Not too difficult to do a regular check, especially as I have a laptop as well.

As I've said before, if we all did things the same way and had the same or similar interests, life would be very boring.....:-)
 Widows defender antivirus slowing PC - No FM2R
Don't get me wrong, I was making no judgement, I just wondered why.

I have certainly noticed that a manual check will sometimes find stuff.

Is there any reason you wouldn't have it on auto and still check manually as and when?
 Widows defender antivirus slowing PC - Stuartli
It's just the routine I've got into over the years - no particular reason either way. So long as updates are installed as and when available, no cause for alarm I feel...:-)
 Widows defender antivirus slowing PC - No FM2R
Hmmm.....

I noticed the computer was running a bit slowly. Not terribly but noticeably.

I checked and realised that Antimalware Executable was hammering the disk

I checked Windows Update, searched for updates and sure enough there were two new ones

I let it install them, which it did with no problems, rebooted and everything was back to normal.

Annoying.
 Widows defender antivirus slowing PC - bathtub tom
I'm finally making some progress on getting my PC back up to speed. I downloaded AVG, I don't know how long it took, but it said it would take a few minutes. After eight hours I went to bed and found it had loaded successfully in the morning. Right away It seemed my PC was faster and looking in task manager windows defender anti-virus was no longer showing. Would AVG kick it out like a cuckoo?

I've found it's not possible to uninstall defender, but I've managed to disable windows defender firewall in services, although it won't let me disable other parts of defender (I get the message 'access denied' and the option is 'greyed out'). I have managed to turn off defender periodic scanning.

When I Google 'uninstall defender', the tutorials give different options to those I can access.

Any suggestions as to what else I can do, or should I be happy I've got my PC back up to speed?
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