IMPORTANT: No additional bug fixes or documentation updates
will be released for this version. For the latest information, see the
current release documentation.
Potential Credential Access via DCSync
editPotential Credential Access via DCSync
editThis rule identifies when a User Account starts the Active Directory Replication Process. Attackers can use the DCSync technique to get credential information of individual accounts or the entire domain, thus compromising the entire domain.
Rule type: eql
Rule indices:
- winlogbeat-*
- logs-system.*
Severity: high
Risk score: 73
Runs every: 5m
Searches indices from: now-9m (Date Math format, see also Additional look-back time
)
Maximum alerts per execution: 100
References:
- https://threathunterplaybook.com/notebooks/windows/06_credential_access/WIN-180815210510.html
- https://threathunterplaybook.com/library/windows/active_directory_replication.html?highlight=dcsync#directory-replication-services-auditing
- https://github.com/SigmaHQ/sigma/blob/master/rules/windows/builtin/security/win_ad_replication_non_machine_account.yml
- https://github.com/atc-project/atomic-threat-coverage/blob/master/Atomic_Threat_Coverage/Logging_Policies/LP_0027_windows_audit_directory_service_access.md
- https://attack.stealthbits.com/privilege-escalation-using-mimikatz-dcsync
- https://www.thehacker.recipes/ad/movement/credentials/dumping/dcsync
Tags:
- Elastic
- Host
- Windows
- Threat Detection
- Credential Access
- Active Directory
Version: 1
Rule authors:
- Elastic
Rule license: Elastic License v2
Investigation guide
edit## Triage and analysis. ### Investigating Active Directory Replication From User Account Active Directory replication is the process by which the changes that originate on one domain controller are automatically transferred to other domain controllers that store the same data. Active Directory data takes the form of objects that have properties, or attributes. Each object is an instance of an object class, and object classes and their respective attributes are defined in the Active Directory schema. The values of the attributes define the object, and a change to a value of an attribute must be transferred from the domain controller on which it occurs to every other domain controller that stores a replica of that object. Adversaries can use the DCSync technique that uses Windows Domain Controller's API to simulate the replication process from a remote domain controller, compromising major credential material such as the Kerberos krbtgt keys used legitimately for tickets creation, but also tickets forging by attackers. This attack requires some extended privileges to succeed (DS-Replication-Get-Changes and DS-Replication-Get-Changes-All), which are granted by default to members of the Administrators, Domain Admins, Enterprise Admins, and Domain Controllers groups. Privileged accounts can be abused to grant controlled objects the right to DCsync/Replicate. More details can be found on [Threat Hunter Playbook](https://threathunterplaybook.com/library/windows/active_directory_replication.html?highlight=dcsync#directory-replication-services-auditing). and [The Hacker Recipes](https://www.thehacker.recipes/ad/movement/credentials/dumping/dcsync) This rule will monitor for Event ID 4662 (Operation was performed on an Active Directory object) and identify events that use the access mask 0x100 (Control Access) and properties that contain at least one of the following or their equivalent Schema-Id-GUID (DS-Replication-Get-Changes, DS-Replication-Get-Changes-All, DS-Replication-Get-Changes-In-Filtered-Set). It also filters out events that use computer accounts and also Azure AD Connect MSOL accounts (more details [here](https://techcommunity.microsoft.com/t5/microsoft-defender-for-identity/ad-connect-msol-user-suspected-dcsync-attack/m-p/788028)). #### Possible investigation steps: - Identify the account that performed the action - Confirm whether the account owner is aware of the operation - Investigate other alerts related to the user/host in the last 48 hours. - Correlate security events 4662 and 4624 (Logon Type 3) by their Logon ID (`winlog.logon.id`) on the Domain Controller (DC) that received the replication request. This will tell you where the AD replication request came from, and if it came from another DC or not. - Investigate which credentials were compromised (e.g. All accounts were replicated or a specific account). ### False Positive Analysis - This activity should not happen legitimately. Any potential B-TP (Benign True Positive) should be mapped and monitored by the security team as replication should be done by Domain Controllers only. Any account that performs this activity can put the domain at risk for not having the same security standards (Long, complex, random passwords that change frequently) as computer accounts, exposing it to credential cracking attacks (Kerberoasting, brute force, etc.). ### Response and Remediation - Initiate the incident response process based on the outcome of the triage - In case of specific credentials were compromised: - Reset the password for the accounts - In case of the entire domain or the `krbtgt` user were compromised: - Activate your incident response plan for total Active Directory compromise which should include, but not be limited to, a password reset (twice) of the `krbtgt` user. ## Config The 'Audit Directory Service Access' logging policy must be configured for (Success, Failure). Steps to implement the logging policy with Advanced Audit Configuration: ``` Computer Configuration > Policies > Windows Settings > Security Settings > Advanced Audit Policies Configuration > Audit Policies > DS Access > Audit Directory Service Access (Success,Failure) ```
Rule query
editany where event.action == "Directory Service Access" and event.code == "4662" and winlog.event_data.Properties : ( /* Control Access Rights/Permissions Symbol */ "*DS-Replication-Get-Changes*", "*DS-Replication-Get-Changes-All*", "*DS-Replication-Get-Changes-In-Filtered-Set*", /* Identifying GUID used in ACE */ "*1131f6ad-9c07-11d1-f79f-00c04fc2dcd2*", "*1131f6aa-9c07-11d1-f79f-00c04fc2dcd2*", "*89e95b76-444d-4c62-991a-0facbeda640c*") /* The right to perform an operation controlled by an extended access right. */ and winlog.event_data.AccessMask : "0x100" and not winlog.event_data.SubjectUserName : ("*$", "MSOL_*")
Framework: MITRE ATT&CKTM
-
Tactic:
- Name: Credential Access
- ID: TA0006
- Reference URL: https://attack.mitre.org/tactics/TA0006/
-
Technique:
- Name: OS Credential Dumping
- ID: T1003
- Reference URL: https://attack.mitre.org/techniques/T1003/
-
Sub-technique:
- Name: DCSync
- ID: T1003.006
- Reference URL: https://attack.mitre.org/techniques/T1003/006/