What is CSRSS?

The Client/Server Runtime Subsystem represents the full-form of the CSRSS. The csrss.exe is a crucial system process as it's a component of the Microsoft Windows NT operating system. It is responsible for creating console windows and managing threads. It is also responsible for providing the user mode side of the Win32 subsystem. In addition to this, it also handles the Win32 subsystem operations that are not in the kernel mode.


Csrss.exe is one of the critical processes of the operating system and so, it cannot be stopped directly from the Task Manager. Also, terminating it affects the behavior of the system as it's a critical process. An important point about csrss.exe is that at any given time, only copy of csrss.exe is running in the system. If you see more than one copy of csrss.exe under the Task Manager, you're most likely to have a virus or a spyware on your system.

Usually, spyware vendors and virus writers make their malware appear as if it's the real Client/Server Runtime Server Subsystem as csrss.exe is an essential component of Microsoft Windows NT operating system. In order to check whether the csrss.exe instance is legitimate or not, you should try to close it from the Task Manager and if it's legitimate then Windows will display a message stating that it's a critical process and cannot be deleted. If the csrss.exe instance is not legitimate then it can be easily terminated from the Task Manager and Windows will not display any message. If the csrss.exe is not legitimate then it should be removed from the system so as to protect the system from attackers.