What Is Mrtstub.exe? Is It Safe in Windows?

If you’ve noticed mrtstub.exe running on your Windows PC and wondered what it does or whether it’s safe, you’re not alone. Many users see this file briefly appear after Windows Update and worry it might be malware.

What Is Mrtstub.exe in Windows?

Mrtstub.exe is a legitimate Windows system file related to Microsoft’s Malicious Software Removal Tool (MSRT).

Its purpose is temporary and specific:

• It launches and prepares MSRT (mrt.exe)
• Helps extract required scan components
• Exits automatically once the scan starts or completes

You’ll usually see it:

• After Windows Update
• During monthly MSRT security scans
• When Windows performs background malware checks

Default file location

C:\Windows\System32\

How Mrtstub.exe Works (Behind the Scenes)

Understanding the process helps remove doubt.

1. Windows Update installs or updates MSRT
2. mrtstub.exe launches as a helper process
3. It extracts and starts mrt.exe
4. MSRT scans the system for known malware
5. Results are logged
6. mrtstub.exe deletes itself automatically

This entire process usually takes a few seconds to a few minutes.

Is Mrtstub.exe Safe or a Virus?

In almost all cases, mrtstub.exe is safe.

It is:

• Developed by Microsoft
• Digitally signed
• Used only during malware scans
• Not a real-time antivirus component

However, like any system file, it can be imitated by malware, which is why verification matters.

How to Check If Mrtstub.exe Is Safe (Important)

Before doing anything, confirm it’s genuine.

Step 1: Check File Location

1. Open Task Manager
2. Right-click mrtstub.exe
3. Click Open file location

If it opens System32, that’s a good sign.

Step 2: Verify Digital Signature

1. Right-click mrtstub.exe
2. Select Properties
3. Open Digital Signatures
4. Confirm signer is Microsoft Windows

If Microsoft is listed, the file is safe.

Step 3: Run a Security Scan (Optional)

• Open Windows Security
• Run a Quick Scan
• Or scan with Malwarebytes

This confirms nothing malicious is hiding behind the name.

How to Run MSRT Manually (Optional but Useful)

You don’t need to wait for Windows Update.

1. Press Win + R
2. Type:mrt
3. Press Enter
4. Choose:
   • Quick Scan
   • Full Scan
   • Custom Scan

This launches the same tool without relying on mrtstub.exe.

How to Fix High CPU or Disk Usage Caused by Mrtstub.exe

Temporary spikes are normal, but prolonged usage needs attention.

Fix 1: Let the Scan Finish

• Full scans can take time
• Especially on older systems or large drives

Fix 2: Restart Your PC (Recommended)

Restarting Windows:

• Clears leftover temporary MSRT files
• Ends stalled background processes
• Resolves most repeated mrtstub.exe appearances

This step is simple but often effective.

Fix 3: Restart Windows Update Services

1. Press Win + R
2. Type:services.msc
3. Restart:
   • Windows Update
   • Background Intelligent Transfer Service

Fix 4: Repair System Files

1. Open Command Prompt (Admin)
2. Run:sfc /scannow

This repairs corrupted system components that may cause MSRT to loop.

How to Reinstall MSRT Safely (Advanced Fix)

If mrtstub.exe keeps reappearing or MSRT behaves abnormally:

1. Download the latest MSRT from Microsoft’s official website
2. Run the installer manually
3. Restart your PC after completion

This refreshes the tool and replaces corrupted components.

Can You Delete Mrtstub.exe?

Manually deleting mrtstub.exe is not recommended.

Why:

• It’s a temporary system file
• Windows recreates it during updates
• Deleting it provides no performance benefit

If Windows removes it automatically, that’s expected behavior.

When Mrtstub.exe Is NOT Safe

Take action if:

• The file runs constantly
• It’s outside System32
• Microsoft is not the signer
• mrt.log is missing
• Antivirus flags it

In such cases:

• Disconnect from the internet
• Run a full antivirus scan
• Remove the file only after confirmation

FAQs Mrtstub.exe

What is mrtstub.exe in Windows?

mrtstub.exe is a legitimate Windows system file used by Microsoft’s Malicious Software Removal Tool to launch malware scans after Windows updates and then remove itself automatically.

Is mrtstub.exe safe or a virus?

mrtstub.exe is safe if it is located in the System32 folder and digitally signed by Microsoft, but malware can imitate the name if the file appears elsewhere.

Why does mrtstub.exe keep appearing and disappearing?

mrtstub.exe appears when MSRT runs during Windows updates or scheduled scans and disappears once the malware scan begins or finishes.

Can I delete mrtstub.exe from my PC?

You should not delete mrtstub.exe manually because it is a temporary Windows file and will be recreated automatically during the next security update.

Does mrtstub.exe cause high CPU usage?

mrtstub.exe can temporarily use CPU or disk resources while MSRT is scanning, but prolonged high usage may indicate a stuck scan or system file issue.

How can I check if mrtstub.exe is legitimate?

You can verify mrtstub.exe by confirming it runs from the System32 folder, checking that it is digitally signed by Microsoft, and ensuring mrt.log exists in the Windows debug folder.

What is mrt.log and why does it matter?

mrt.log is the log file created by the Malicious Software Removal Tool, and its presence confirms that mrtstub.exe is performing a legitimate malware scan.

How do I run MSRT without waiting for Windows Update?

You can manually run the Malicious Software Removal Tool by pressing Win + R, typing mrt, and pressing Enter.

Does mrtstub.exe replace antivirus software?

mrtstub.exe does not replace antivirus software because it only removes known malware and does not provide real-time protection.

Why does Windows reinstall mrtstub.exe after updates?

Windows reinstalls mrtstub.exe as part of regular security updates to ensure the Malicious Software Removal Tool remains current.

When should mrtstub.exe be considered suspicious?

mrtstub.exe should be investigated if it runs constantly, appears outside System32, lacks a Microsoft digital signature, or triggers antivirus warnings.

Can mrtstub.exe be disabled permanently?

mrtstub.exe cannot be safely disabled because it is integrated with Windows security updates and malware cleanup processes.

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Mrtstub.exe is a legitimate Windows process used to launch Microsoft’s Malicious Software Removal Tool. In normal conditions, you should let it run and exit on its own.