I think it is Lsass.exe
Windows NT4/2000/XP only. LSASS is the Local Security Authentication Server. It verifies the validity of user logons to your PC/Server (in technical jargon : it generates the process that is responsible for authenticating users for the Winlogon service).
An integral part of the operating system, leave alone.
Source: click here
I wouldn't allow access to it!