Antimalware Service Executable High CPU Windows 11 Fix [2026]

Quick Answer: MsMpEng.exe uses high CPU during real-time scanning. Add exclusions for folders you trust and set scan schedule to run when PC is idle.

Symptoms

MsMpEng.exe using 50-100% CPU
System slows down randomly
Happens during file operations
Fans spin up frequently

Root Cause

Real-time scanning every file access, large file scans, or conflicting AV software.

Fix

Method 1: Add Exclusions

Windows Security → Virus protection → Manage settings
Exclusions → Add folder
Exclude: Downloads, Dev folders, large media libraries

Method 2: Limit CPU Usage

Get-ItemProperty -Path "HKLM:\SOFTWARE\Policies\Microsoft\Windows Defender\Scan" -Name "AvgCPULoadFactor" -ErrorAction SilentlyContinue

Set to 30-50% max.

Method 3: Schedule Scans

Task Scheduler → Microsoft → Windows → Windows Defender
Modify scan to run at 3 AM when idle

Method 4: Check for Conflicting AV

Uninstall third-party antivirus if using Windows Defender.

How Againly Helps

Againly runs check_third_party_av to detect AV conflicts and scan overhead.

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Related: 100% Disk Usage Fix

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