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4733(S): A member was removed from a security-enabled local group.

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Event 4733 illustration

Subcategory: Audit Security Group Management

Event Description:

This event generates every time member was removed from security-enabled (security) local group.

This event generates on domain controllers, member servers, and workstations.

For every removed member you will get separate 4733 event.

You will typically see “4735: A security-enabled local group was changed.” event without any changes in it prior to 4733 event.

Note  For recommendations, see Security Monitoring Recommendations for this event.


Event XML:

- <Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
- <System>
 <Provider Name="Microsoft-Windows-Security-Auditing" Guid="{54849625-5478-4994-A5BA-3E3B0328C30D}" /> 
 <EventID>4733</EventID> 
 <Version>0</Version> 
 <Level>0</Level> 
 <Task>13826</Task> 
 <Opcode>0</Opcode> 
 <Keywords>0x8020000000000000</Keywords> 
 <TimeCreated SystemTime="2015-08-19T16:51:00.376806500Z" /> 
 <EventRecordID>175037</EventRecordID> 
 <Correlation /> 
 <Execution ProcessID="520" ThreadID="1524" /> 
 <Channel>Security</Channel> 
 <Computer>DC01.contoso.local</Computer> 
 <Security /> 
 </System>
- <EventData>
 <Data Name="MemberName">CN=Auditor,CN=Users,DC=contoso,DC=local</Data> 
 <Data Name="MemberSid">S-1-5-21-3457937927-2839227994-823803824-2104</Data> 
 <Data Name="TargetUserName">AccountOperators</Data> 
 <Data Name="TargetDomainName">CONTOSO</Data> 
 <Data Name="TargetSid">S-1-5-21-3457937927-2839227994-823803824-6605</Data> 
 <Data Name="SubjectUserSid">S-1-5-21-3457937927-2839227994-823803824-1104</Data> 
 <Data Name="SubjectUserName">dadmin</Data> 
 <Data Name="SubjectDomainName">CONTOSO</Data> 
 <Data Name="SubjectLogonId">0x35e38</Data> 
 <Data Name="PrivilegeList">-</Data> 
 </EventData>
 </Event>

Required Server Roles: None.

Minimum OS Version: Windows Server 2008, Windows Vista.

Event Versions: 0.

Field Descriptions:

Subject:

  • Security ID [Type = SID]: SID of account that requested the “remove member from the group” operation. Event Viewer automatically tries to resolve SIDs and show the account name. If the SID cannot be resolved, you will see the source data in the event.

Note  A security identifier (SID) is a unique value of variable length used to identify a trustee (security principal). Each account has a unique SID that is issued by an authority, such as an Active Directory domain controller, and stored in a security database. Each time a user logs on, the system retrieves the SID for that user from the database and places it in the access token for that user. The system uses the SID in the access token to identify the user in all subsequent interactions with Windows security. When a SID has been used as the unique identifier for a user or group, it cannot ever be used again to identify another user or group. For more information about SIDs, see Security identifiers.

  • Account Name [Type = UnicodeString]: the name of the account that requested the “remove member from the group” operation.

  • Account Domain [Type = UnicodeString]: subject’s domain or computer name. Formats vary, and include the following:

    • Domain NETBIOS name example: CONTOSO

    • Lowercase full domain name: contoso.local

    • Uppercase full domain name: CONTOSO.LOCAL

    • For some well-known security principals, such as LOCAL SERVICE or ANONYMOUS LOGON, the value of this field is “NT AUTHORITY”.

    • For local user accounts, this field will contain the name of the computer or device that this account belongs to, for example: “Win81”.

  • Logon ID [Type = HexInt64]: hexadecimal value that can help you correlate this event with recent events that might contain the same Logon ID, for example, “4624: An account was successfully logged on.”

Member:

  • Security ID [Type = SID]: SID of account that was removed from the group. Event Viewer automatically tries to resolve SIDs and show the group name. If the SID cannot be resolved, you will see the source data in the event.

  • Account Name [Type = UnicodeString]: distinguished name of account that was removed from the group. For example: “CN=Auditor,CN=Users,DC=contoso,DC=local”. For local groups this field typically has “-“ value, even if removed member is a domain account. For some well-known security principals, such as LOCAL SERVICE or ANONYMOUS LOGON, the value of this field is “-”.

Note  The LDAP API references an LDAP object by its distinguished name (DN). A DN is a sequence of relative distinguished names (RDN) connected by commas.

An RDN is an attribute with an associated value in the form attribute=value; . These are examples of RDNs attributes:

• DC - domainComponent

• CN - commonName

• OU - organizationalUnitName

• O - organizationName

Group:

  • Security ID [Type = SID]: SID of the group from which the member was removed. Event Viewer automatically tries to resolve SIDs and show the group name. If the SID cannot be resolved, you will see the source data in the event.

  • Group Name [Type = UnicodeString]: the name of the group from which the member was removed. For example: ServiceDesk

  • Group Domain [Type = UnicodeString]: domain or computer name of the group from which the member was removed. Formats vary, and include the following:

    • Domain NETBIOS name example: CONTOSO

    • Lowercase full domain name: contoso.local

    • Uppercase full domain name: CONTOSO.LOCAL

    • For a local group, this field will contain the name of the computer to which this new group belongs, for example: “Win81”.

Additional Information:

  • Privileges [Type = UnicodeString]: the list of user privileges which were used during the operation, for example, SeBackupPrivilege. This parameter might not be captured in the event, and in that case appears as “-”. See full list of user privileges in “Table 8. User Privileges.”.

Security Monitoring Recommendations

For 4733(S): A member was removed from a security-enabled local group.

Type of monitoring required Recommendation
Removal of members from local or domain security groups: You might need to monitor the removal of members from local or domain security groups. If you need to monitor each time a member is removed from a local or domain security group, to see who added the member and when, monitor this event.
Typically, this event is used as an informational event, to be reviewed if needed.
High-value local or domain security groups: You might have a list of critical local or domain security groups in the organization, and need to specifically monitor these groups for the removal of members (or for other changes).
Examples of critical local or domain groups are built-in local administrators group, domain admins, enterprise admins, and so on.		 Monitor this event with the “Group\Group Name” values that correspond to the high-value local or domain security groups.
Local or domain security groups with required members: You might need to ensure that for certain local or domain security groups, particular members are never removed. Monitor this event with the “Group\Group Name” that corresponds to the group of interest, and the “Member\Security ID” of the members who should not be removed.
High-value accounts: You might have high-value domain or local accounts for which you need to monitor each action.
Examples of high-value accounts are database administrators, built-in local administrator account, domain administrators, service accounts, domain controller accounts and so on.		 Monitor this event with the “Subject\Security ID” and “Member\Security ID” that correspond to the high-value account or accounts.
Anomalies or malicious actions: You might have specific requirements for detecting anomalies or monitoring potential malicious actions. For example, you might need to monitor for use of an account outside of working hours. When you monitor for anomalies or malicious actions, use the “Subject\Security ID” (with other information) to monitor how or when a particular account is being used.
Non-active accounts: You might have non-active, disabled, or guest accounts, or other accounts that should never be used. Monitor this event with the “Subject\Security ID” and “Member\Security ID” that correspond to the accounts that should never be used.
Account allowlist: You might have a specific allowlist of accounts that are the only ones allowed to perform actions corresponding to particular events. If this event corresponds to an “allowlist-only” action, review the “Subject\Security ID” for accounts that are outside the allowlist.
Accounts of different types: You might want to ensure that certain actions are performed only by certain account types, for example, local or domain account, machine or user account, vendor or employee account, and so on. If this event corresponds to an action you want to monitor for certain account types, review the “Subject\Security ID” to see whether the account type is as expected.
External accounts: You might be monitoring accounts from another domain, or “external” accounts that are not allowed to perform certain actions (represented by certain specific events). Monitor this event for the “Subject\Account Domain” corresponding to accounts from another domain or “external” accounts.
Restricted-use computers or devices: You might have certain computers, machines, or devices on which certain people (accounts) should not typically perform any actions. Monitor the target Computer: (or other target device) for actions performed by the “Subject\Security ID” that you are concerned about.
Account naming conventions: Your organization might have specific naming conventions for account names. Monitor “Subject\Account Name” for names that don’t comply with naming conventions.