What is csrss.exe process and why it is running and using high cpu?

CSRSS.exe stands for Client Server Runtime Sub System and is an essential process to run Windows properly as it is responsible for majority of graphical instruction sets, console windows, creating and deleting threads and some parts in 16 bit virtual MS-DOS environment.

Csrss.exe in windows xp , windows 7 - vista and windows 8

It must be running all the time and is a very essential and critical process for Windows, termination of this process can result in blue screen error, thats why its not listed in startup entries and can not be killed / terminated from task manager. If you try to kill the process you would get an error saying access denied.

error while killing csrss.exe process

This file csrss.exe is considered as safe as it is inbuilt in Windows and is from Microsoft itself.

In certain conditions csrss.exe may be corrupted and may be a virus as described below.

WHY CSRSS.EXE IS USING 100% CPU OR HIGH CPU AND HOW TO FIX IT ?

It is the case of corrupt Microsoft Windows Profile and not due to virus. You may fix the corrupt Windows profile by deleting and recreating it. Here is how to do this :

  1. Backup : First you need to backup all files in My Documents folder as they all will be lost. Any other personal or important file should also be backed up prior to do this.
  2. Login as another user account (must have administrator privileges): Now you need to logout from the user that is creating the problem and login as a different user account in the windows (if you do not have another account you need to create a new user account in control panel).
  3. Deleting the corrupted profile : Now you need to find the corrupted user profile and delete it. Here is how to do that :-
    • Right click on My Computer icon and open Properties.
      open properties to fix csrss.exe
    • Go to Advance tab.
      open advance tab to fix csrss error
    • Under advance settings tab open Settings button.
      open profiles under advance tab to fix csrss.exe
    • There in Settings, find User profiles and delete the corrupted user profile (should be named as same as the user account of that user).

      deleting the corrupted user profile to fix csrss.exe error
      Fig: deleting the corrupted user profile
    • After deleting, create a new user account under Control Panel with the same name as it was previously.
    • Copy all the files back to My Documents backed prior to starting.

IS CSRSS.EXE IS A VIRUS / MALWARE/ TROJAN ?

Csrss.exe is inbuilt in Windows from Microsoft and is not a virus / malware. It is considered to be safe and and a critically essential file for Windows to work properly.

However any file can got corrupted due to virus and malware so is the case with csrss.exe file. So the answer is:

YES, CSRSS.EXE IS A VIRUS AND A MALWARE IF :

  • More than two instances of csrss.exe are running on your computer. Go to task manager to find it.
  • The location of csrss.exe file is different than
    C:\Windows\Sysytem32

    csrss is a virus if path is different than this
    Fig: correct path of csrss.exe, otherwise it may be a virus.
  • (If the process file resides in any other location than above then it is a virus.)

So if any one condition above is met then yes csrss.exe is corrupted on your computer and may be a virus / malware.

NO, CSRSS.EXE IS NOT A VIRUS IF :

  • It is using 100% cpu ( it is the case of corrupted user profile, just fix it as described above).
  • Location of file is
    C:\Windows\System32

KNOWN VARIANTS OF CSRSS.EXE VIRUS AND WHAT IT DOES ?

If somehow your csrss.exe file got corrupted by a virus or malware then it may be one of the following virus :

  • Trojan.W32.Rontokbro
  • Trojan.W32.Sober
  • Trojan.W32.Beagle
  • Trojan.W32.VIRKEL
  • Trojan.W32.Dropper

There may be other variants also that may be undiscovered till the writing of this post as on 13th September 2014.

Trojan virus may be very dangerous to your computer as it may harm in following ways :

  • Stealing passwords
  • Remote access your computer by a hacker
  • Stealing internet banking data and information such as credit card numbers, etc.
  • Slow down your computer
  • Blue screen to death error

It must be removed as soon as possible from your computer.

HOW TO REMOVE CSRSS.EXE VIRUS?

You may use popular anti virus softwares to scan your system and remove any virus if found then. One thing to be noted here is that always download any anti virus software from its official site only or cnet. Please double check the site address before downloading any thing.

I personally recommend free or paid version of AVG anti virus as it is very lite and only put loads on cpu when needed. You can download avg anti virus from its official site. here it is

AVG anti virus – http://www.avg.com

If the above information on csrss.exe file/process helps you in any way then do not forget to like, comment and share.

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