csrss.exe is a program which is probably legit. So, if csrss.exe is on your system, it is probably ok, and will NOT be a cause for concern. Even if your PC is clean, it is still recommended to use a good antivirus with a good detection rate, in order to yourself your system against threats.
This application is normally found in C:\Windows\System32\csrss.exe.
The MD5 checksum for this program is 31e45caa8e7035ecd47e96a7377be975.
This application is NOT registered as a Windows service. This is good.
csrss.exe seems to use the functions of Windows SFC (System File Checker) or Windows File Protection.
This is a x64 executable. It runs using the full capacity of modern CPUs.
csrss.exe is digitally signed. Nowadays most legit software applications are digitally signed.
The digital signature attached to csrss.exe is valid. This is most likely a clean, ok program.
Digital certificate name: Microsoft Windows Publisher
Certificate's issuer name: Microsoft Windows Production PCA 2011
This executable does NOT have a removal routine set up in registry.