What Is Csrss.exe?

This Windows process performs important functions behind the scenes

The csrss.exe file, which shows up in Task Manager as Client Server Runtime Process, is an essential part of Windows. You never interact with it directly as a user. Still, it performs some essential functions in the background, whether you use Windows 10, Windows 8, or Windows 7.

Under normal circumstances, the csrss.exe file isn't malware or a virus, which means you can't safely delete or quarantine it. However, there is an easy way to verify whether you're dealing with the actual csrss.exe or an imposter. If your system has been infected with malware pretending to be csrss.exe, then the best course of action is to remove it.

What Is Client Server Runtime Process?

When you open the Task Manager on any Windows computer, you'll find at least one instance, and often several instances, of something called Client Server Runtime Process. This is the display name that Windows uses for csrss.exe, which stands for client server runtime subsystem.

The Client Server Runtime Process has been around since the early days of Windows. Before 1996, it was responsible for the graphical subsystem. That use has changed throughout the years, but it's still responsible for some critical work behind the scenes in Windows 10, Windows 8, and Windows 7.

The Client Server Runtime Process displayed in Task Manager on a desktop Windows computer.

Tetra Images / Getty Images

Is It Safe to Disable Csrss.exe?

Even though csrss.exe has limited functionality in modern versions of Windows, compared to obsolete versions, it's still critical. That means you can't kill, disable, delete, or quarantine csrss.exe without experiencing severe consequences.

If you kill a legitimate csrss.exe process, your system may become unstable. In most cases, your computer will shut down. The computer typically starts up fine afterward, but deleting or quarantining the file may result in a computer that is unusable without professional intervention.

What Causes Csrss.Exe to Use Excessive GPU or CPU?

Under normal circumstances, csrss.exe should only use a small amount of system resources. If you open Task Manager and see an instance of Client Server Runtime Process using an excessive amount of system resources like CPU, GPU, or memory, that usually indicates some type of problem.

If you're using Windows 7, you should disable Aero. If you're using Windows 10 or Windows 8, update your graphics drivers or roll back to an earlier driver if you updated recently.

In most cases, the cause behind csrss.exe using excessive resources is that you're dealing with a fake.

Could Csrss.exe Be a Virus?

While csrss.exe is a legitimate file and an essential part of Windows, some malware and viruses sneak through with fake names. That means it's possible to have malware that uses the csrss.exe file name or slight variations of that name.

If you suspect that your computer may be infected with a csrss.exe virus or malware, it's easy to figure that out. This is because legitimate copies of the csrss.exe file are only found in two different folders.

If you find a Client Server Runtime Process in your Task Manager that points to any other folder or to a file that isn't named csrss.exe, that means you have some type of malware or virus.

New malware and viruses appear all the time, but the Nimda.E virus in particular is known to use the csrss.exe file name.

Here's how to tell if an instance of Client Server Runtime process is legitimate:

  1. Press and hold CTRL+Alt+Del, and select Open task manager.

  2. Select the Processes tab.

    Windows Task Manager with the Processes tab highlighted.
  3. Scroll down to the Windows processes section.

    Windows Task Manager Windows Processes section.
  4. Tap-and-hold or right-click Client Server Runtime Process, and select Open file location.

    Windows Task Manager highlighting Open file location.
  5. Verify that the csrss.exe process is located in your %SystemRoot%\System32 or %SystemRoot%\SysWOW64 folder.

    Windows System32 folder.

    If the file is located anywhere else or isn't named csrss.exe, you may be dealing with malware or a virus. Pay close attention to the file name. If one letter is different from csrss.exe, it's probably malware.

  6. Repeat these steps for each instance of Client Server Runtime Process that you see in your Task Manager.

What to Do if You Think Malware Is Masquerading as Csrss.exe

If you suspect that you have malware or a virus running on your computer that's disguised as an innocuous Client Server Runtime Process, the best thing to do is to scan your computer for malware.

While you can safely delete a csrss.exe file if it's located outside your System32 or SysWOW64 folder, doing so may not actually remove the malware. If you opt to delete such a file, always scan your computer afterward with at least one free spyware or malware removal tool.

In some situations, you may find that you can't delete the malicious csrss.exe file or that you have malware that actively prevents you from running a malware removal tool. In those cases, you'll want to use a bootable antivirus tool on a flash drive or CD.

  • What is a csrss.exe Trojan?

    The csrss.exe Trojan is a malware file masquerading as a csrss.exe file. This malicious application can steal your personal data and lead to data loss and identity theft. If you suspect you have a csrss.exe Trojan, use a reputable antivirus application to perform a full system scan to scan your computer for malware.

  • Why do I have two csrss.exe files running?

    If you see two instances of csrss.exe files running on your computer, it's possible one is a legitimate Client Server Runtime Process and one is malware. If you suspect malware, use a reputable antivirus application to perform a full system scan. It's also possible that you have two csrss.exe files running because there are other users logged on; check to see if other users are in a session.

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