What is MsMpEng.exe?

The genuine MsMpEng.exe file is a software component of Windows Defender by Microsoft Corporation.
"MsMpEng.exe" is Microsoft's core antimalware executable. It performs the actual background real-time protective scanning for malware, viruses, and worms of files that it detects as having been created or updated recently. It has been used since Windows XP both in consumer-oriented products, (Windows Defender, Microsoft Security Essentials), and by Microsoft enterprise products designed for managed software or server environments such as Forefront Client Security (FCS), meant only for Windows Server, not endpoint Windows. High CPU usage is a well-known side-effect of "msmpeng.exe", often a major reason that users install third-party antimalware products. When such products are installed, Windows Defender is deactivated. It installs in a subdirectory of "C:\Program Files" whose name depends on the OS version: "\Microsoft Security Client" for XP/Vista/Win7, or "\Windows Defender" for Win8/8.1/10. It is uninstalled if the overall security product name is removed via the Control Panel.

MsMPEng stands for Microsoft Malware Protection Engine

The .exe extension on a filename indicates an executable file. Executable files may, in some cases, harm your computer. Therefore, please read below to decide for yourself whether the MsMpEng.exe on your computer is a Trojan that you should remove, or whether it is a file belonging to the Windows operating system or to a trusted application.

Click to Run a Free Scan for MsMpEng.exe related errors

MsMpEng.exe file information

Windows Task Manager with MsMpEng
MsMpEng.exe process in Windows Task Manager

The process known as Antimalware Service Executable or Service Executable or AntiMalware Service Executable or Microsoft Antimalware belongs to software Microsoft Malware Protection or Microsoft Windows Operating System or Microsoft Security Essentials or Windows Defender or Microsoft Antimalware Service or Microsoft Antimalware or Microsoft Antimalware Package or Deployd by Microsoft ( or Deployd.

Description: MsMpEng.exe is not essential for the Windows OS and causes relatively few problems. MsMpEng.exe is located in a subfolder of "C:\Program Files"—primarily C:\Program Files\Microsoft Security Client\. Known file sizes on Windows 10/8/7/XP are 11,736 bytes (9% of all occurrences), 23,808 bytes and 71 more variants. 
The process runs as service WinDefend. The service helps protect users from malware and other potentially unwanted software.
The program has no visible window. MsMpEng.exe is certified by a trustworthy company. MsMpEng.exe is not a Windows system file. Therefore the technical security rating is 19% dangerous, but you should also take into account the user reviews.

Uninstalling this variant: In case of problems with MsMpEng.exe, you may also do the following:

Recommended: Identify MsMpEng.exe related errors

Important: Some malware camouflages itself as MsMpEng.exe, particularly when located in the C:\Windows or C:\Windows\System32 folder. Therefore, you should check the MsMpEng.exe process on your PC to see if it is a threat. We recommend Security Task Manager for verifying your computer's security. This was one of the Top Download Picks of The Washington Post and PC World.


User Comments

it is so bad it makes a virus
Windows Defender on win 10
  Ingo B.  
While the process can hog CPU usage and RAM, the process itself is safe. It is part of Microsoft Security Essentials. Beware of fake versions, however.
Windows Defender
Takes 100% of my disk space while im playing games.
MSmpeNG key found in Registry: "HKCU\SW\MS\Win\Current Version\RUN" pointing to "C:\Users\ username \AppData\Romaing\svc-xorl.exe" found by Malwarebytes as "Rogue.FakeAV"
Resource hog, but not spyware or virus... safe to kill it if you don't plan on downloading any viruses.
More comments can be found here:
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Rating chart

Summary: Average user rating of MsMpEng.exe: based on 207 votes with 9 reviews. 117 users think MsMpEng.exe is essential for Windows or an installed application. 15 users think it's probably harmless. 26 users think it's neither essential nor dangerous. 15 users suspect danger. 34 users think MsMpEng.exe is dangerous and recommend removing it. 21 users don't grade MsMpEng.exe ("not sure about it").

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Best practices for resolving MsMpEng issues

A clean and tidy computer is the key requirement for avoiding problems with MsMpEng. This means running a scan for malware, cleaning your hard drive using 1cleanmgr and 2sfc /scannow, 3uninstalling programs that you no longer need, checking for Autostart programs (using 4msconfig) and enabling Windows' 5Automatic Update. Always remember to perform periodic backups, or at least to set restore points.

Should you experience an actual problem, try to recall the last thing you did, or the last thing you installed before the problem appeared for the first time. Use the 6resmon command to identify the processes that are causing your problem. Even for serious problems, rather than reinstalling Windows, you are better off repairing of your installation or, for Windows 8 and later versions, executing the 7DISM.exe /Online /Cleanup-image /Restorehealth command. This allows you to repair the operating system without losing data.

To help you analyze the MsMpEng.exe process on your computer, the following programs have proven to be helpful: ASecurity Task Manager displays all running Windows tasks, including embedded hidden processes, such as keyboard and browser monitoring or Autostart entries. A unique security risk rating indicates the likelihood of the process being potential spyware, malware or a Trojan. BMalwarebytes Anti-Malware detects and removes sleeping spyware, adware, Trojans, keyloggers, malware and trackers from your hard drive.

Other processes

MsMpEng.exe [all]