How to Fix High CPU Usage Caused by Antimalware Service Executable on Windows 11

Summary

This guide helps you troubleshoot and resolve: How to Fix High CPU Usage Caused by Antimalware Service Executable on Windows 11. Follow the steps below to fix the issue.

Common Causes

If your Windows 11 computer feels sluggish or fans are running loudly, high CPU usage from the Antimalware Service Executable may be the cause. This process is part of Microsoft Defender Antivirus, which runs in the background to protect your system from malware and other threats. While occasional spikes are normal during scans or definition updates, sustained high usage can impact productivity for small business and home office users. This guide walks you through steps to reduce CPU load and restore normal performance.

Quick Fix Steps

1. Restart your computer to clear temporary processes and pending updates.
2. Check for and install any available Windows updates.
3. Run a full malware scan to rule out actual infections causing high resource usage.
4. If CPU usage remains high after restarting, proceed to the detailed instructions below.

Detailed Instructions

1. Schedule Windows Defender scans outside business hours

By default, Windows Defender may run scheduled scans during active work hours, causing noticeable CPU spikes. You can adjust scan timing using Task Scheduler.

1. Press Windows key + S, type Task Scheduler, and press Enter.
2. In the left pane, expand Task Scheduler Library, then Microsoft, then Windows, and select Windows Defender.
3. In the centre pane, locate Windows Defender Scheduled Scan.
4. Right-click Windows Defender Scheduled Scan and select Properties.
5. Go to the Triggers tab and click Edit.
6. Change the schedule to a time when your computer is on but not in active use, such as overnight or during lunch breaks.
7. Click OK, then click OK again to save the changes.

2. Exclude specific folders from real-time scanning

If you work with large files, databases, or development projects, excluding non-essential folders from real-time protection can reduce CPU load. Only exclude folders you trust.

1. Click the Start button and select Settings.
2. Select Privacy & security from the left menu.
3. Click Windows Security, then click Open Windows Security.
4. Select Virus & threat protection.
5. Under Virus & threat protection settings, click Manage settings.
6. Scroll to Exclusions and click Add or remove exclusions.
7. Click Add an exclusion, choose Folder, and select the directory you want to exclude.
8. Click Select Folder to confirm.

3. Check for conflicting third-party antivirus software

Running another antivirus product alongside Microsoft Defender can cause conflicts and high CPU usage. Windows 11 usually disables Defender automatically when it detects a third-party solution, but remnants of old software can still cause issues.

1. Click Start, then select Settings.
2. Go to Apps > Installed apps.
3. Look for any antivirus programs you no longer use, such as expired trial versions of Norton, McAfee, or Avast.
4. Click the three dots (...) next to the program and select Uninstall.
5. Follow the prompts to remove the software, then restart your computer.

4. Update Windows and Microsoft Defender definitions

Outdated definition files or missing Windows updates can cause Defender to work inefficiently.

1. Open Settings.
2. Select Windows Update from the left menu.
3. Click Check for updates.
4. Install any available updates and restart your computer if prompted.
5. Open Windows Security > Virus & threat protection.
6. Under Virus & threat protection updates, click Check for updates to ensure definition files are current.

5. Perform a clean boot (advanced)

If high CPU usage persists, a third-party application or service may be conflicting with Windows Defender. A clean boot starts Windows with a minimal set of drivers and startup programs.

1. Press Windows key + R, type msconfig, and press Enter.
2. Go to the Services tab.
3. Check Hide all Microsoft services.
4. Click Disable all, then click Apply.
5. Go to the Startup tab and click Open Task Manager.
6. In Task Manager, disable each enabled startup item by right-clicking it and selecting Disable.
7. Close Task Manager and click OK in the System Configuration window.
8. Restart your computer.

After restarting, monitor CPU usage. If the issue is resolved, re-enable services and startup items one by one to identify the conflicting program.

Troubleshooting

CPU usage remains high after all steps

If the Antimalware Service Executable continues to use high CPU after following this guide, there may be an underlying system issue or malware infection that requires professional assistance.

If you need further assistance, please Open a Ticket with our Brisbane support team.

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