The !sid extension displays the security identifier (SID) at the specified address.
!sid Address [Flags]
Specifies the address of the SID structure.
If this is set to 1, the SID type, domain, and user name for the SID is displayed.
If this is set to 1, the friendly name is displayed. This includes the SID type, as well as the domain and user name for the SID.
For information about SIDs, see the Microsoft Windows SDK documentation, the Windows Driver Kit (WDK) documentation, or Microsoft Windows Internals by Mark Russinovich and David Solomon. Also see !sd and !acl.
Here are two examples, one without the friendly name shown, and one with:
kd> !sid 0xe1bf35b8 SID is: S-1-5-21-518066528-515770016-299552555-513 kd> !sid 0xe1bf35b8 1 SID is: S-1-5-21-518066528-515770016-299552555-513 (Group: MYGROUP\Domain Users)