Set Windows Defender Antivirus Max CPU Usage for a Scan in Windows 10  

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    Set Windows Defender Antivirus Max CPU Usage for a Scan in Windows 10

    Set Windows Defender Antivirus Max CPU Usage for a Scan in Windows 10

    How to Change Windows Defender Antivirus Maximum CPU Usage for a Scan in Windows 10
    Published by Category: Security System
    06 Jul 2020
    Designer Media Ltd



    How to Change Windows Defender Antivirus Maximum CPU Usage for a Scan in Windows 10


    Windows Security is built-in to Windows 10 and includes an antirvirus program called Windows Defender Antivirus.

    Windows Defender Antivirus helps protect your PC against malware (malicious software) like viruses, spyware, and other potentially unwanted software. Malware can infect your PC without your knowledge: it might install itself from an email message, when you connect to the Internet, or when you install certain apps using a USB flash drive, CD, DVD, or other removable media. Some malware can also be programmed to run at unexpected times, not only when it's installed.

    Windows Defender Antivirus has a maximum 50 percentage CPU usage for a scan by default in Windows 10. If you like, you can specify a percentage of CPU usage you want Windows Defender Antivirus to not exceed.

    See also: Configure Windows Defender Antivirus scanning options | Microsoft Docs

    This tutorial will show you how to specify the maximum percentage CPU usage allowed for a scan by Windows Defender Antivirus in Windows 10.

    You must be signed in as an administrator to specify maximum percentage CPU usage for a scan by Windows Defender Antivirus.



    Contents

    • Option One: To See Current Maximum CPU Usage for Scan by Windows Defender Antivirus
    • Option Two: To Specify Maximum CPU Usage for Scan by Windows Defender Antivirus in PowerShell
    • Option Three: To Specify Maximum CPU Usage for Scan by Windows Defender Antivirus in Local Group Policy Editor
    • Option Four: To Specify Maximum CPU Usage for Scan by Windows Defender Antivirus using a REG file for Local Group Policy






    OPTION ONE

    To See Current Maximum CPU Usage for Scan by Windows Defender Antivirus


    1 Open an elevated PowerShell.

    2 Copy and paste the command below into the elevated PowerShell, and press Enter. (see screenshot below)

    Get-MpPreference | select ScanAvgCPULoadFactor

    3 You will now see the ScanAvgCPULoadFactor value (ex: "50") for the current maximum percentage CPU usage for a scan.

    4 You can now close the elevated PowerShell window if you like.

    Set Windows Defender Antivirus Max CPU Usage for a Scan in Windows 10-scanavgcpuloadfactor-1.png






    OPTION TWO

    To Specify Maximum CPU Usage for Scan by Windows Defender Antivirus in PowerShell


    This option will set the AvgCPULoadFactor DWORD value in the HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Defender\Scan key in Registry Editor.


    1 Open an elevated PowerShell.

    2 Type the command below into the elevated PowerShell, and press Enter. (see screenshot below)

    Set-MpPreference -ScanAvgCPULoadFactor <percentage>

    Substitute <percentage> in the command above with a value of 5 to 100 for the maximum CPU usage you want to specify.

    Setting a value of 0 will disable CPU throttling for Windows Defender Antivirus allowing Windows Defender Antivirus to use as much CPU as it wants.

    50 is the default value.

    For example: Set-MpPreference -ScanAvgCPULoadFactor 50

    3 You can now close the elevated PowerShell window if you like.

    Set Windows Defender Antivirus Max CPU Usage for a Scan in Windows 10-scanavgcpuloadfactor-2.png






    OPTION THREE

    To Specify Maximum CPU Usage for Scan by Windows Defender Antivirus in Local Group Policy Editor


    The Local Group Policy Editor is only available in the Windows 10 Pro, Enterprise, and Education editions.

    If the policy in this option is enabled to specify, it will override Option Two.

    All editions can use Option Two or Option Four.


    1 Open the Local Group Policy Editor.

    2 In the left pane of Local Group Policy Editor, navigate to the location below. (see screenshot below)

    Computer Configuration/Administrative Templates/Windows Components/Windows Defender Antivirus/Scan

    Set Windows Defender Antivirus Max CPU Usage for a Scan in Windows 10-avgcpuloadfactor_gpedit-1.png

    3 In the right pane of Scan in Local Group Policy Editor, double click/tap on the Specify the maximum percentage of CPU utilization during a scan policy to edit it. (see screenshot above)

    4 Do step 5 (specify) or step 6 (undo) below for what you would like to do.


     5. To Enable Policy to Specify Maximum CPU Usage for Scan by Windows Defender Antivirus

    A) Select (dot) Enabled. (see screenshot below)

    B) Under Options, type a value of 5 to 100 for the maximum CPU usage you want to specify, click/tap on OK, and go to step 7 below.

    Setting a value of 0 will disable CPU throttling for Windows Defender Antivirus allowing Windows Defender Antivirus to use as much CPU as it wants.

    50 is the default value.


     6. To Undo Policy to Not Specify Maximum CPU Usage for Scan by Windows Defender Antivirus

    A) Select (dot) Not Configured or Disabled, click/tap on OK, and go to step 7 below. (see screenshot below)

    Not Configured is the default setting.

    Set Windows Defender Antivirus Max CPU Usage for a Scan in Windows 10-avgcpuloadfactor_gpedit-2.png

    7 When finished, you can close the Local Group Policy Editor if you like.






    OPTION FOUR

    To Specify Maximum CPU Usage for Scan by Windows Defender Antivirus using a REG file for Local Group Policy


    The option is for the same policy as Option Three.

    If the policy in this option is enabled to specify, it will override Option Two.


    1 Press the Win + R keys to open the Run dialog, type regedit into Run, and click/tap on OK to open Registry Editor.

    2 Navigate to the key below in the left pane of Registry Editor. (see screenshot below)

    HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows Defender\Scan

    If you do not have a Scan key, then right click on the Windows Defender key, click/tap on New, click/tap on Key, type Scan for the name, and press Enter.


    Set Windows Defender Antivirus Max CPU Usage for a Scan in Windows 10-avgcpuloadfactor_regedit-1.png

    3 Do step 4 (specify) or step 5 (undo) below for what you would like to do.


     4. To Enable Policy to Specify Maximum CPU Usage for Scan by Windows Defender Antivirus

    A) In the right pane of the Scan key, double click/tap on the AvgCPULoadFactor DWORD value to modify it. (see screenshot below step 2)

    If you do not have a AvgCPULoadFactor DWORD, then right click on an empty area in the right pane of the Scan key, click/tap on New, click/tap on DWORD (32-bit) Value, type AvgCPULoadFactor for the name, and press Enter.


    B) Select (dot) Decimal, type a value of 5 to 100 for the maximum CPU usage you want to specify, click/tap on OK, and go to step 6. (see screenshot below)

    Setting a value of 0 will disable CPU throttling for Windows Defender Antivirus allowing Windows Defender Antivirus to use as much CPU as it wants.

    50 is the default value.


    Set Windows Defender Antivirus Max CPU Usage for a Scan in Windows 10-avgcpuloadfactor_regedit-2.png


     5. To Undo Policy to Not Specify Maximum CPU Usage for Scan by Windows Defender Antivirus

    A) In the right pane of the Scan key, right click on the AvgCPULoadFactor DWORD value, and click/tap on Delete. (see screenshot below step 2)

    B) Click/tap on Yes to confirm, and go to step 6. (see screenshot below)

    Set Windows Defender Antivirus Max CPU Usage for a Scan in Windows 10-avgcpuloadfactor_regedit-3.png

    6 You can now close Registry Editor if you like.


    That's it,
    Shawn





  1. Posts : 1,244
    Windows 10 Pro x64 21H2 (Build: 19044.1415)
       #1

    Hello Brink, it looks like this setting has no effect on mpengine.

    I've tried all of the options you described and even after system reboot my scan consumes 100% of CPU.

    There is one thing I noticed though:
    In "Option 2" you say: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Defender\Scan
    But GPO sets: HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows Defender\Scan

    However none of these 2 keys work so I guess you made a typo here.

    Anyway is there any workaround for this?

    - - - Updated - - -

    Here is screenshot to confirm:

    Set Windows Defender Antivirus Max CPU Usage for a Scan in Windows 10-untitled.png

    EDIT:
    Removed wrong registry entry screenshot.
      My Computer


  2. Posts : 61,585
    64-bit Windows 11 Pro for Workstations
    Thread Starter
       #2

    Hello @zebal,

    The PowerShell command uses: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Defender\Scan

    The GPO will override and uses: HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows Defender\Scan

    Did you test running a scan from within Windows Security to see what percentage it uses?
      My Computers


  3. Posts : 1,244
    Windows 10 Pro x64 21H2 (Build: 19044.1415)
       #3

    Sorry for confusion, I said "mpengine" but I didn't run scan from command line.
    The scan test I did was: Windows Security -> Scan options -> Custom scan
    And my CPU usage skyrockets to maximum.
    Are you able to reproduce this?

    Brink said:
    The PowerShell command uses: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Defender\Scan

    The GPO will override and uses: HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows Defender\Scan
    Ah OK, didn't know, it makes sense.
      My Computer


  4. Posts : 61,585
    64-bit Windows 11 Pro for Workstations
    Thread Starter
       #4

    zebal said:
    Sorry for confusion, I said "mpengine" but I didn't run scan from command line.
    The scan test I did was: Windows Security -> Scan options -> Custom scan
    And my CPU usage skyrockets to maximum.
    Are you able to reproduce this?.
    I barely go above 10% with a quick scan.
      My Computers


  5. Posts : 1,244
    Windows 10 Pro x64 21H2 (Build: 19044.1415)
       #5

    Ah you got it!
    It works well for quick scans but not for custom scan.

    Same problem with insider build, so I think I'll just go ahead and report this problem.

    But if you're aware of a workaround let me know, because right now my scans are more like CPU stress tests rather than virus scans

    - - - Updated - - -

    Full scan also does not respect setting.
      My Computer


  6. Posts : 61,585
    64-bit Windows 11 Pro for Workstations
    Thread Starter
       #6

    zebal said:
    Ah you got it!
    It works well for quick scans but not for custom scan.

    Same problem with insider build, so I think I'll just go ahead and report this problem.

    But if you're aware of a workaround let me know, because right now my scans are more like CPU stress tests rather than virus scans

    - - - Updated - - -

    Full scan also does not respect setting.
    Interesting. You would think it should get applied to all scan types.
      My Computers


  7. Posts : 1,244
    Windows 10 Pro x64 21H2 (Build: 19044.1415)
       #7

    The policy setting says:
    "This policy setting allows you to configure the maximum percentage CPU utilization permitted during a scan"

    It says nothing about scan type.

    What am I missing?
      My Computer


  8. Posts : 61,585
    64-bit Windows 11 Pro for Workstations
    Thread Starter
       #8

    zebal said:
    The policy setting says:
    "This policy setting allows you to configure the maximum percentage CPU utilization permitted during a scan"

    It says nothing about scan type.

    What am I missing?
    Nothing. It makes one believe it should be applied to all scan types. Odd bug.
      My Computers


  9. Posts : 1,244
    Windows 10 Pro x64 21H2 (Build: 19044.1415)
       #9

    Well I guess you're right, it's a bug with policy description and not with anti virus

    So you think this works as it should?
      My Computer


 

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