Launcher process
runexehelper.exe c:\windows\system32\calc.exe
Launches the specified exe. Prerequisites: (1) diagtrack_action_output environment variable must be set to an existing, writable folder; (2) runexewithargs_output.txt file cannot exist in the folder indicated by the variable.
Executes arbitrary code
c:\windows\system32\runexehelper.exe
Sigma: https://github.com/SigmaHQ/sigma/blob/197615345b927682ab7ad7fa3c5f5bb2ed911eed/rules/windows/process_creation/proc_creation_win_lolbin_runexehelper.yml, IOC: c:\windows\system32\runexehelper.exe is run, IOC: Existence of runexewithargs_output.txt file
Grzegorz Tworek (@0gtweet)