Antimalware Service Executable eats memory
Antimalware Service Executable high memory how to fix
Written by The CommonFixes team · fact checked by CommonFixes review desk
Last updated
Short answer
Antimalware Service Executable is the working part of Microsoft Defender, the antivirus built into Windows. It is meant to be busy sometimes: during a scheduled scan, straight after an update, or while you copy a lot of files. It becomes a problem when scans keep starting at awkward moments, when it keeps re-scanning huge folders that never change, or when a second antivirus is installed and the two keep checking each other's work. The quickest thing to try first: let one full scan finish before judging it — Open Windows Security, Virus and threat protection, Scan options, choose Full scan and let it run to the end, ideally overnight. A scan that keeps being interrupted starts again from the beginning every time, which is why some machines feel slow all week. Most people are done in about 20 minutes.
Full walkthrough below: 6 steps for Windows, rated easy.
Sounds like this
- •Antimalware Service Executable near the top of Task Manager
- •The fan runs while you are not doing anything
- •Everything feels sluggish for an hour after you switch on
Why it happens
Antimalware Service Executable is the working part of Microsoft Defender, the antivirus built into Windows. It is meant to be busy sometimes: during a scheduled scan, straight after an update, or while you copy a lot of files. It becomes a problem when scans keep starting at awkward moments, when it keeps re-scanning huge folders that never change, or when a second antivirus is installed and the two keep checking each other's work.
Work through these in order
0% done- 1
Let one full scan finish before judging it
Open Windows Security, Virus and threat protection, Scan options, choose Full scan and let it run to the end, ideally overnight. A scan that keeps being interrupted starts again from the beginning every time, which is why some machines feel slow all week.
- 2
Move the scheduled scan to a time you are not working
Open Task Scheduler, go to Task Scheduler Library, Microsoft, Windows, Windows Defender. Double click Windows Defender Scheduled Scan, open the Conditions tab and tick Start the task only if the computer is idle, then set a time on the Triggers tab such as two in the morning.
- 3
Cap how much processor it may use
Open Terminal as administrator and run Set-MpPreference -ScanAvgCPULoadFactor 20. That tells Defender to keep its average use near twenty percent. It is an official setting, so nothing is being disabled or weakened.
- 4
Exclude folders that are large and safe
Windows Security, Virus and threat protection, Manage settings, Exclusions, Add an exclusion. Good candidates are virtual machine folders, game libraries, video project folders and programming project folders. Never exclude your Downloads folder or a whole drive, because that is where risky files actually arrive.
- 5
Remove any second antivirus
If Avast, McAfee, Norton or similar is installed alongside, uninstall the one you do not want through Settings, Apps, and use the maker's own removal tool afterwards. Two live scanners on one machine is a classic cause of constant disk and memory use.
- 6
Check for a real infection
If it stays high right after a clean start with nothing open, run an offline scan: Windows Security, Virus and threat protection, Scan options, Microsoft Defender Antivirus Offline Scan. The machine restarts and scans before Windows loads, which catches things that hide while Windows is running.
If none of that worked
Do not turn Defender off permanently through the registry. Windows turns real time protection back on by itself, and a machine left unprotected costs far more time later than a slow morning does. If the computer only has four gigabytes of memory, Defender is not really the problem: adding memory or moving to a solid state drive will change how the whole machine feels.
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The CommonFixes team
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This guide was last updated on 10 August 2026. If a step no longer matches what you see on screen, tell us on the contact page and we will test it again.
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