OS Credential Dumping: DCSync
Other sub-techniques of OS Credential Dumping (8)
Adversaries may attempt to access credentials and other sensitive information by abusing a Windows Domain Controller's application programming interface (API)[1] [2] [3] [4] to simulate the replication process from a remote domain controller using a technique called DCSync.
Members of the Administrators, Domain Admins, and Enterprise Admin groups or computer accounts on the domain controller are able to run DCSync to pull password data[5] from Active Directory, which may include current and historical hashes of potentially useful accounts such as KRBTGT and Administrators. The hashes can then in turn be used to create a Golden Ticket for use in Pass the Ticket[6] or change an account's password as noted in Account Manipulation.[7]
DCSync functionality has been included in the "lsadump" module in Mimikatz.[8] Lsadump also includes NetSync, which performs DCSync over a legacy replication protocol.[9]
Procedure Examples
| Name | Description |
|---|---|
| Mimikatz |
Mimikatz performs credential dumping to obtain account and password information useful in gaining access to additional systems and enterprise network resources. It contains functionality to acquire information about credentials in many ways, including from DCSync/NetSync.[11][8][12][13] |
Mitigations
| Mitigation | Description |
|---|---|
| Active Directory Configuration |
Manage the access control list for "Replicating Directory Changes" and other permissions associated with domain controller replication.[5][10] |
| Password Policies |
Ensure that local administrator accounts have complex, unique passwords across all systems on the network. |
| Privileged Account Management |
Do not put user or admin domain accounts in the local administrator groups across systems unless they are tightly controlled, as this is often equivalent to having a local administrator account with the same password on all systems. Follow best practices for design and administration of an enterprise network to limit privileged account use across administrative tiers. |
Detection
Monitor domain controller logs for replication requests and other unscheduled activity possibly associated with DCSync.[1] [2] [3] Also monitor for network protocols[1] [9] and other replication requests[14] from IPs not associated with known domain controllers.[15]
Note: Domain controllers may not log replication requests originating from the default domain controller account.[16]
References
- Microsoft. (2017, December 1). MS-DRSR Directory Replication Service (DRS) Remote Protocol. Retrieved December 4, 2017.
- Microsoft. (n.d.). IDL_DRSGetNCChanges (Opnum 3). Retrieved December 4, 2017.
- SambaWiki. (n.d.). DRSUAPI. Retrieved December 4, 2017.
- Wine API. (n.d.). samlib.dll. Retrieved December 4, 2017.
- Metcalf, S. (2015, September 25). Mimikatz DCSync Usage, Exploitation, and Detection. Retrieved August 7, 2017.
- Schroeder, W. (2015, September 22). Mimikatz and DCSync and ExtraSids, Oh My. Retrieved August 7, 2017.
- Warren, J. (2017, July 11). Manipulating User Passwords with Mimikatz. Retrieved December 4, 2017.
- Deply, B., Le Toux, V. (2016, June 5). module ~ lsadump. Retrieved August 7, 2017.
- Microsoft. (2017, December 1). MS-NRPC - Netlogon Remote Protocol. Retrieved December 6, 2017.
- Microsoft. (n.d.). How to grant the "Replicating Directory Changes" permission for the Microsoft Metadirectory Services ADMA service account. Retrieved December 4, 2017.
- Deply, B. (n.d.). Mimikatz. Retrieved September 29, 2015.
- Grafnetter, M. (2015, October 26). Retrieving DPAPI Backup Keys from Active Directory. Retrieved December 19, 2017.
- The Australian Cyber Security Centre (ACSC), the Canadian Centre for Cyber Security (CCCS), the New Zealand National Cyber Security Centre (NZ NCSC), CERT New Zealand, the UK National Cyber Security Centre (UK NCSC) and the US National Cybersecurity and Communications Integration Center (NCCIC). (2018, October 11). Joint report on publicly available hacking tools. Retrieved March 11, 2019.
- Microsoft. (n.d.). MS-SAMR Security Account Manager (SAM) Remote Protocol (Client-to-Server) - Transport. Retrieved December 4, 2017.
- Metcalf, S. (2015, September 25). Mimikatz DCSync Usage, Exploitation, and Detection. Retrieved December 4, 2017.
- Schroeder, W. (2015, September 22). Mimikatz and DCSync and ExtraSids, Oh My. Retrieved December 4, 2017.