What Is A Windows Security Identifier (SID)?
Intro
A security identifier (SID) is a unique value of variable length that is used to identify a security principal (such as a security group) in Windows operating systems. SIDs that identify generic users or generic groups is particularly well-known. Their values remain constant across all operating systems.
Documentation
Tips and Tidbits
A security identifier (SID) is used to uniquely identify a security principal or security group.
Security principals can represent any entity that can be authenticated by the operating system, such as a user account, a computer account, or a thread or process that runs in the security context of a user or computer account.
The SID for a local account or group is generated by the Local Security Authority (LSA) on the computer, and it is stored with other account information in a secure area of the registry.
The SID for a domain account or group is generated by the domain security authority, and it is stored as an attribute of the User or Group object in Active Directory Domain Services.
For every local account and group, the SID is unique for the computer where it was created.
No two accounts or groups on the computer ever share the same SID.
Likewise, for every domain account and group, the SID is unique within an enterprise.
This means that the SID for an account or group that is created in one domain will never match the SID for an account or group created in any other domain in the enterprise.
SIDs always remain unique.
Security authorities never issue the same SID twice, and they never reuse SIDs for deleted accounts.
SIDs of Active Directory objects are stored in the
ntds.ditdatabase, and SIDs of local users and groups in the local Windows Security Account Manager (SAM) database in theHKEY_LOCAL_MACHINE\SAM\SAMregistry key.
Well-Known SID Structures
For example, given a SID defined in the table below as S-1-5-21-<domain>-513, and the actual instance of the domain having the three sub authority values of 1, 2, and 3:
S-1: Indicates a revision or version 1 SID.
5: SECURITY_NT_AUTHORITY, indicates it's a Windows specific SID.
21: SECURITY_NT_NON_UNIQUE, indicates a domain id (or local computer identifer) will follow.
1-2-3: The next three SubAuthority arrays contain 32-bit random numbers to uniquely identify the domain.
RID: Indicates a unique object ID within the domain.
The actual constructed SID would be S-1-5-21-1-2-3-513.
Well-known SIDs (all versions of Windows)
All versions of Windows use the following well-known SIDs.
SID | Name | Description |
S-1-0 | Null Authority | An identifier authority. |
S-1-0-0 | Nobody | No security principal. |
S-1-1 | World Authority | An identifier authority. |
S-1-1-0 | Everyone | A group that includes all users, even anonymous users and guests. Membership is controlled by the operating system. Note |
S-1-2 | Local Authority | An identifier authority. |
S-1-2-0 | Local | A group that includes all users who have logged on locally. |
S-1-3 | Creator Authority | An identifier authority. |
S-1-3-0 | Creator Owner | A placeholder in an inheritable access control entry (ACE). When the ACE is inherited, the system replaces this SID with the SID for the object's creator. |
S-1-3-1 | Creator Group | A placeholder in an inheritable ACE. When the ACE is inherited, the system replaces this SID with the SID for the primary group of the object's creator. The primary group is used only by the POSIX subsystem. |
S-1-3-4 | Owner Rights | A group that represents the current owner of the object. When an ACE that carries this SID is applied to an object, the system ignores the implicit READ_CONTROL and WRITE_DAC permissions for the object owner. |
S-1-4 | Non-unique Authority | An identifier authority. |
S-1-5 | NT Authority | An identifier authority. |
S-1-5-1 | Dialup | A group that includes all users who have logged on through a dial-up connection. Membership is controlled by the operating system. |
S-1-5-2 | Network | A group that includes all users that have logged on through a network connection. Membership is controlled by the operating system. |
S-1-5-3 | Batch | A group that includes all users that have logged on through a batch queue facility. Membership is controlled by the operating system. |
S-1-5-4 | Interactive | A group that includes all users that have logged on interactively. Membership is controlled by the operating system. |
S-1-5-5-X-Y | Logon Session | A logon session. The X and Y values for these SIDs are different for each session. |
S-1-5-6 | Service | A group that includes all security principals that have logged on as a service. Membership is controlled by the operating system. |
S-1-5-7 | Anonymous | A group that includes all users that have logged on anonymously. Membership is controlled by the operating system. |
S-1-5-9 | Enterprise Domain Controllers | A group that includes all domain controllers in a forest that uses an Active Directory directory service. Membership is controlled by the operating system. |
S-1-5-10 | Principal Self | A placeholder in an inheritable ACE on an account object or group object in Active Directory. When the ACE is inherited, the system replaces this SID with the SID for the security principal who holds the account. |
S-1-5-11 | Authenticated Users | A group that includes all users whose identities were authenticated when they logged on. Membership is controlled by the operating system. |
S-1-5-12 | Restricted Code | This SID is reserved for future use. |
S-1-5-13 | Terminal Server Users | A group that includes all users that have logged on to a Terminal Services server. Membership is controlled by the operating system. |
S-1-5-14 | Remote Interactive Logon | A group that includes all users who have logged on through a terminal services logon. |
S-1-5-17 | This Organization | An account that is used by the default Internet Information Services (IIS) user. |
S-1-5-18 | Local System | A service account that is used by the operating system. |
S-1-5-19 | NT Authority | Local Service |
S-1-5-20 | NT Authority | Network Service |
S-1-5-21-domain-500 | Administrator | A user account for the system administrator. By default, it is the only user account that is given full control over the system. |
S-1-5-21-domain-501 | Guest | A user account for people who do not have individual accounts. This user account does not require a password. By default, the Guest account is disabled. |
S-1-5-21-domain-502 | KRBTGT | A service account that is used by the Key Distribution Center (KDC) service. |
S-1-5-21-domain-512 | Domain Admins | A global group whose members are authorized to administer the domain. By default, the Domain Admins group is a member of the Administrators group on all computers that have joined a domain, including the domain controllers. Domain Admins is the default owner of any object that is created by any member of the group. |
S-1-5-21-domain-513 | Domain Users | A global group that, by default, includes all user accounts in a domain. When you create a user account in a domain, it is added to this group by default. |
S-1-5-21-domain-514 | Domain Guests | A global group that, by default, has only one member, the domain's built-in Guest account. |
S-1-5-21-domain-515 | Domain Computers | A global group that includes all clients and servers that have joined the domain. |
S-1-5-21-domain-516 | Domain Controllers | A global group that includes all domain controllers in the domain. New domain controllers are added to this group by default. |
S-1-5-21-domain-517 | Cert Publishers | A global group that includes all computers that are running an enterprise certification authority. Cert Publishers are authorized to publish certificates for User objects in Active Directory. |
S-1-5-21-root domain-518 | Schema Admins | A universal group in a native-mode domain; a global group in a mixed-mode domain. The group is authorized to make schema changes in Active Directory. By default, the only member of the group is the Administrator account for the forest root domain. |
S-1-5-21-root domain-519 | Enterprise Admins | A universal group in a native-mode domain; a global group in a mixed-mode domain. The group is authorized to make forest-wide changes in Active Directory, such as adding child domains. By default, the only member of the group is the Administrator account for the forest root domain. |
S-1-5-21-domain-520 | Group Policy Creator Owners | A global group that is authorized to create new Group Policy objects in Active Directory. By default, the only member of the group is Administrator. |
S-1-5-21-domain-526 | Key Admins | A security group. The intention for this group is to have delegated write access on the msdsKeyCredentialLink attribute only. The group is intended for use in scenarios where trusted external authorities (for example, Active Directory Federated Services) are responsible for modifying this attribute. Only trusted administrators should be made a member of this group. |
S-1-5-21-domain-527 | Enterprise Key Admins | A security group. The intention for this group is to have delegated write access on the msdsKeyCredentialLink attribute only. The group is intended for use in scenarios where trusted external authorities (for example, Active Directory Federated Services) are responsible for modifying this attribute. Only trusted administrators should be made a member of this group. |
S-1-5-21-domain-553 | RAS and IAS Servers | A domain local group. By default, this group has no members. Servers in this group have Read Account Restrictions and Read Logon Information access to User objects in the Active Directory domain local group. |
S-1-5-32-544 | Administrators | A built-in group. After the initial installation of the operating system, the only member of the group is the Administrator account. When a computer joins a domain, the Domain Admins group is added to the Administrators group. When a server becomes a domain controller, the Enterprise Admins group also is added to the Administrators group. |
S-1-5-32-545 | Users | A built-in group. After the initial installation of the operating system, the only member is the Authenticated Users group. When a computer joins a domain, the Domain Users group is added to the Users group on the computer. |
S-1-5-32-546 | Guests | A built-in group. By default, the only member is the Guest account. The Guests group allows occasional or one-time users to log on with limited privileges to a computer's built-in Guest account. |
S-1-5-32-547 | Power Users | A built-in group. By default, the group has no members. Power users can create local users and groups; modify and delete accounts that they have created; and remove users from the Power Users, Users, and Guests groups. Power users also can install programs; create, manage, and delete local printers; and create and delete file shares. |
S-1-5-32-548 | Account Operators | A built-in group that exists only on domain controllers. By default, the group has no members. By default, Account Operators have permission to create, modify, and delete accounts for users, groups, and computers in all containers and organizational units of Active Directory except the Builtin container and the Domain Controllers OU. Account Operators do not have permission to modify the Administrators and Domain Admins groups, nor do they have permission to modify the accounts for members of those groups. |
S-1-5-32-549 | Server Operators | A built-in group that exists only on domain controllers. By default, the group has no members. Server Operators can log on to a server interactively; create and delete network shares; start and stop services; back up and restore files; format the hard disk of the computer; and shut down the computer. |
S-1-5-32-550 | Print Operators | A built-in group that exists only on domain controllers. By default, the only member is the Domain Users group. Print Operators can manage printers and document queues. |
S-1-5-32-551 | Backup Operators | A built-in group. By default, the group has no members. Backup Operators can back up and restore all files on a computer, regardless of the permissions that protect those files. Backup Operators also can log on to the computer and shut it down. |
S-1-5-32-552 | Replicators | A built-in group that is used by the File Replication service on domain controllers. By default, the group has no members. Do not add users to this group. |
S-1-5-32-582 | Storage Replica Administrators | A built-in group that grants complete and unrestricted access to all features of Storage Replica. |
S-1-5-64-10 | NTLM Authentication | An SID that is used when the NTLM authentication package authenticated the client. |
S-1-5-64-14 | SChannel Authentication | An SID that is used when the SChannel authentication package authenticated the client. |
S-1-5-64-21 | Digest Authentication | An SID that is used when the Digest authentication package authenticated the client. |
S-1-5-80 | NT Service | An NT Service account prefix. |
How To Get My User’s SID
All SIDs start with S-1-5-21
The SID for the Administrator account in Windows always ends in 500.
The SID for the Guest account always ends in 501.
wmic useraccount get name,sid
Name SID
Administrator S-1-5-21-65601276-2964384289-692651738-500
DefaultAccount S-1-5-21-65601276-2964384289-692651738-503
Guest S-1-5-21-65601276-2964384289-692651738-501
Roger S-1-5-21-65601276-2964384289-692651738-1001
WDAGUtilityAccount S-1-5-21-65601276-2964384289-692651738-504
Getting The Local Machine’s SID
A good comprehensive article: How to Convert SID to User/Group Name and User to SID?
The SID of the local computer (Machine SID) can be obtained using the PsGetSID tool (https://docs.microsoft.com/en-us/sysinternals/downloads/psgetsid ). But you have to download and install the tool on each computer manually.
.\PsGetsid64.exe
Or simply by trimming the last 4 characters (RID) from the SID of any local user:
$user=(Get-LocalUser Administrator).sid$user -replace ".{4}$"
cd C:\Users\Roger\Downloads\PSTools
PS C:\Users\Roger\Downloads\PSTools> .\PsGetsid64.exe
PsGetSid v1.45 - Translates SIDs to names and vice versa
Copyright (C) 1999-2016 Mark Russinovich
Sysinternals - www.sysinternals.com
SID for \\GOLDEN-IMAGE:
S-1-5-21-65601276-2964384289-692651738
PS C:\Users\Roger\Downloads\PSTools> $user=(Get-LocalUser Administrator).sid
>> $user -replace ".{4}$"
S-1-5-21-65601276-2964384289-692651738
PS C:\Users\Roger\Downloads\PSTools>
(Get-LocalUser Administrator).sid | ft AccountDomainSid, Value
AccountDomainSid Value
---------------- -----
S-1-5-21-65601276-2964384289-692651738 S-1-5-21-65601276-2964384289-692651738-500
It is important that each computer in the domain has a unique local (machine) SID. If you are cloning computers or virtual machines or creating them from a template, you must run the sysprep utility before joining them to the domain. This tool resets the local Machine SID. This will save you from common trust relationship errors.
Get The Domain SID
If a Windows computer is joined to an Active Directory domain, it will have two different SIDs. The first SID is the local computer identifier (Machine SID), and the second is the unique computer object identifier in AD.
You can get the SID of a computer in the Active Directory domain using the command:
Get-ADComputer <computer name> -properties sid|select name,sid
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