Microsoft Client Runtime Server Subsystem

• Csrss.exe is a process used by the Microsoft Client Runtime Server Subsystem to manage various graphical instruction sets in the Windows operating system. The process is considered a critical system process and thus terminating it can cause significant system failures, including the Blue Screen of Death, a state where your computer screen turns completely blue and your system shuts down.
  
  

Malicious?

• Csrss.exe is installed and used by several malicious programs, including Win-Spy, ICE Remote Spy, KidWatcher, Buddy Pro and W32.Backdoor.Sokacaps. All of these programs slow your computer and reduce your available system memory. In addition, some of these programs steal the personal information stored on your computer, including visited websites and online banking passwords, and send it to remote hackers.
  
  

End Process

• Before ending csrss.exe, determine whether the instance of csrss.exe running on your computer belongs to Microsoft Client Runtime Server or a malicious program. To do this, press "Ctrl," "Shift" and "Escape" to open the Windows Task Manager. Click the "Processes" tab and the "Show Processes From All Users" button. Right-click "csrss.exe" and click "Properties." Click on the "General" tab in the "Properties" window. Next to "Location" it should say "C:\Windows." If it doesn't, the instance of csrss.exe doesn't belong to Microsoft and thus most likely belongs to a malicious program. To end the process, right-click "csrss.exe" and click "End Process."
  
  

Warning

• Ending a malicious csrss.exe process won't remove the malicious program that's using the process from your computer. Thus, in addition to ending the process, run an up-to-date anti-malware program. There are several free anti-malware programs available online, including Microsoft Security Essentials, Avast! Free Antivirus 6 and AVG Antivirus Free Edition 2011.