If you've ever checked the Windows Task Manager to see why your computer is running so slow, you might have noticed a process called Antimalware Service Executable using a lot of the available CPU or memory.

The Antimalware Service Executable, or MsMpEng.exe, is part of the Windows Security suite that ships with Windows 10. Windows Security includes everything from anti-malware tools, to a firewall, account management and protection services, and more.

Your computer might run slowly at certain times because Windows Security is doing an automated malware detection scan. Occasionally this scan might run into issues with certain files, folders, or software, even if they're secure.

In this article we'll go over a few things you can do to improve Windows Security's performance.

#1: Check for third-party anti-malware software

It's generally recommended that you only run one anti-malware/anti-virus/anti-spyware software on your PC at a time.

Running Windows Security and third-party software like Malwarebytes together can cause issues where they both recognize each other as potential threats. This can lead to situations where neither works properly.

Windows Security is considered to be very secure, so it's safe to remove third-party security software. Simply uninstall the third party software and reboot your computer.

Then to check that Windows Security is running, press the Windows key, type in "windows security", and click on "Windows Security" to open the app:

How to open the Windows Security app in the Windows Start Menu
Open the Windows Security app

Click on "Virus & threat protection", and click "Manage settings" under "Virus & threat protection settings":

Screenshot of the Virus & threat protection menu
The Virus & threat protection menu

Once in the "Virus & threat protection settings" menu, ensure that the "Real-time protection" toggle is on:

Check that the "Real-time" protection toggle is on

Alternatively, if you'd like to use third-party security software, just install and configure that first. Then repeat the steps above and turn the "Real-time protection" toggle off.

This will prevent Windows Security from scanning and potentially flagging your third-party software as insecure.

#2: Prevent Windows Security from scanning certain files and folders

As mentioned earlier, Windows Security can sometimes run into issues while scanning certain files, folders, and executable programs.

Though you do want Windows Security to scan as much of your system as possible, there are some things you can safely exclude to reduce the amount of CPU and memory it uses.

Prevent Windows Security from scanning MsMpEng.exe

The first thing you can try is to prevent the Antimalware Service Executable process from scanning itself.

Press the Windows key, type in "windows security", and click on "Windows Security" to open the Windows Security app.

Click on "Virus & threat protection", and click on "Manage settings" under "Virus & threat protection settings":

Screenshot of the "Virus & threat protection" menu
The "Virus & threat protection" menu

In the "Virus & threat protection settings" menu, scroll down to "Exclusions" and click on "Add or remove exclusions":

Screenshot of the "Add or remove exclusions" button

Then click the plus button with the text "Add an exclusion", and click "File":

Screenshot of selecting "File" from the "Exclusions" menu

Then in the File Explorer window, select C:\Program Files\Windows Defender\MsMpEng and click "Open":

Screenshot selecting MsMpEng

Now Windows Security will skip over the Antimalware Service Executable/MsMpEng.exe file while scanning for malware, and should use less available CPU and memory than before.

Prevent Windows Security from scanning the Windows Defender directory

Similar to the last method of skipping over the Antimalware Service Executable, it's possible to exclude the entire Windows Defender directory from anti-malware scans.

Follow the steps from the last method, but after clicking the "Add an exclusion" button, select "Folder" instead:

Screenshot of selecting "Folder" from the "Exclusions" menu

Then in the File Explorer window that pops up, select C:\Program Files\Windows Defender and click "Select Folder":

Screenshot selecting Windows Defender folder

And now Windows Security will skip over everything in the Windows Defender folder, including the MsMpEng.exe file itself.

#3: Consider upgrading your PC

If none of the other solutions work, it might be worth upgrading parts of your PC. As of 2020, new PCs are often configured with at least 8 GB of RAM and a solid-state drive (SSD) rather than an older hard disk drive (HDD). And increasingly, software is written with those minimum specs in mind.

If your computer is older and has less RAM and a slower HDD, consider adding more RAM and doing a clean install of Windows 10 on an SSD.

This won't solve the issue of the Antimalware Service Executable using 100% of the CPU, but more RAM and a faster SSD will ensure that anti-malware scans are completed much faster overall. Also, you'll find that everything from booting your computer to opening and saving files is much faster than before.

While PC upgrades are outside the scope of this tutorial, it's worth considering as an option – just a couple new (or used!) parts can make an older computer feel like an entirely different machine.

In summary

There are a bunch of reasons why the Antimalware Service Executable/MsMpEng.exe could cause a system to slow down. But usually it'll only use a lot of the available CPU and memory when it's scanning for malware.

So really the trick is to speed up the malware scan itself – check for conflicting security software, limit the files and folders it has to scan, or consider upgrading your PC's hardware.

Did any of these methods work for you? Or did you find something else that solved the issue? Either way, let me know on Twitter.