# Windows - Knowledge base & Tips

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Published 2025-12-03

# Security Identifier (SID)

Identify Entities
Unique Value
SID for local and groups accounts generated by LSA
SID for domain user and groups generated by DC
Cannot be changed

S-R-X-Y

S - Literal "S" which indicates that the string is a SID
R - Revision, always set to 1, initial version
X - Identifier Authority. "5" means NT Authority for local
Y - Sub authority. Domain ID and Relative ID (RID)

# Well Known SIDs

RID under 1000
Generic Built-in groups and users

S-1-0-0                       Nobody        
S-1-1-0	                      Everybody
S-1-5-18                      Local System
S-1-5-11                      Authenticated Users
S-1-5-domainidentifier-500    Administrator