Sign up for the ITPro Today newsletter
Stay on top of the IT universe with commentary, news analysis, how-to's, and tips delivered to your inbox daily.
Q: What are the exact roles of a Windows account's SID, and more specifically its RID, for Windows security?
Windows security-related processes use security IDs (SIDs) to uniquely identify security principals. The Relative ID (RID) uniquely identifies a security principal relative to the local or domain security authority that issued the SID.
Jan De Clercq
October 21, 2011
2 Min Read
A: Every Windows user, computer, or service account has a unique alphanumeric identifier called the security ID (SID). Windows security-related processes, such as authentication, authorization, delegation, and auditing, use SIDs to uniquely identify security principals. Because SIDs are used by system processes, the format of a SID—unlike the format of a logon name—isn't user- or administrator-friendly.
To illustrate, let us analyze an example SID that I retrieved from my test Active Directory (AD) system: S-1-5-21-4064627337-2434140041-2375368561-1036. All SID fields have a specific meaning; so, for the above sample SID:
S: The initial S identifies the following string as a SID.
1: The revision level, or version, of the SID specification. To date, this has never changed and has always been 1.
5: The identifier authority value. This is a predefined identifier for the top-level authority that issued the SID. This is typically 5, which represents the SECURITY_NT_AUTHORITY.
21-4064627337-2434140041-2375368561: This section is the domain or local computer identifier (in this example, a domain identifier). This is a 48-bit string that identifies the authority (the computer or domain) that created the SID.
1036: The Relative ID (RID) is the last part of a SID. The RID uniquely identifies a security principal relative to the local or domain security authority that issued the SID. Any group or user that the Windows OS doesn't create has a RID of 1000 or greater by default.
The SID of an AD domain account is created by a domain's security authority that runs on every Windows domain controller (DC). The SID of a local account is created by the Local Security Authority (LSA) service that runs on every Windows box.
An important property of a SID is its uniqueness in time and place. A SID is unique in the environment where it was created (in a domain or on a local computer). It's also unique in time: If you create a user object, delete it, then recreate it with the same name, the new object won't have the same SID as the original object.
About the Author
You May Also Like
.png?width=700&auto=webp&quality=80&disable=upscale)