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Malware hoaxes
There are numerous virus hoaxes that claim that csrss.exe is malware and should be removed to prevent damage to the system; these are false, as removing csrss.exe or killing the csrss.exe process will result in a Blue Screen of Death.
In addition, technical support scammers pretending to be Microsoft representatives are known to use csrss.exe as "proof" of a virus infection, and convince the user being scammed into purchasing their rogue security software to remove it.[1]
Technical details
CSRSS runs as a user-mode system service. When a user-mode process calls a function involving console windows, process/thread creation, or side-by-side support, instead of issuing a system call, the Win32 libraries (kernel32.dll, user32.dll, gdi32.dll) send an inter-process call to the CSRSS process which does most of the actual work without compromising the kernel.[2] Window manager and GDI services are handled by a kernel mode driver (win32k.sys) instead.[3]
CSRSS is called along with winlogon.exe at Windows start-up. If either of the files is corrupted or otherwise inaccessible, the NT kernel will shut down the start-up process with a Blue Screen of Death. This is caused by a failure to move out of kernel mode and into user mode, the "normal" operation of Windows. The error code for this fault is 0xc000021a.
In Windows 7 and later, instead of drawing console windows itself, CSRSS spawns conhost.exe subprocesses to draw console windows for command line programs with the permissions of that user.
History
The Windows NT 3.x series of releases had placed the Graphics Device Interface component in CSRSS, but this was moved into kernel mode with Windows NT 4.0 to improve graphics performance.[4] The Windows startup process has changed significantly since Vista. Two instances of csrss.exe are running in Windows 7 and Vista.[5]
See also
References
- ^ Cimpanu, Catalin (Jan 22, 2016). "Symantec Disavows Business Partner Caught Running a Tech Support Scam". Softpedia. Retrieved July 29, 2016.
- ^ "Detailed implementation of a system service in Windows NT". Undocumented Windows NT. Retrieved 2010-06-10.
- ^ Russinovich, Mark (2009). Windows Internals, 5th Edition. Microsoft Press. p. 54.
- ^ "The Windows NT 4.0 Kernel mode change". MS Windows NT Kernel-mode User and GDI White Paper. Microsoft. Retrieved 2009-01-19.
- ^ "Inside the Windows Vista Kernel – Startup Processes". Inside the Windows Vista Kernel – Startup Processes. Microsoft. Retrieved 2010-10-01.