What is it?
Local Security Authentication Server - lsass.exe

What does it do?
lsass.exe - It generates the process responsible for authenticating users for the Winlogon service. This process is performed by using authentication packages such as the default Msgina.dll. If authentication is successful, Lsass generates the user's access token, which is used to launch the initial shell. Other processes that the user initiates inherit this token.

You will not be able to end this through task manager!

From MS

---

The lsass.exe which is from Microsoft is located at c:windowsSystem32lsass.exe . there's a few viruses that have been found to run as lsass.exe to hide from you.