Performing Active Directory Compromise Investigation

Overview

Active Directory (AD) compromise investigation is a critical incident response capability that focuses on identifying how attackers gained access to domain services, what persistence mechanisms they established, and the scope of credential compromise. Since 88% of breaches involve compromised credentials (Verizon 2025 DBIR), AD is the primary target for enterprise-wide attacks. Investigators must analyze NTDS.dit database integrity, Kerberos ticket-granting activity, Group Policy modifications, replication metadata, and privileged group membership changes to reconstruct the attack chain and determine full compromise scope.

Key Investigation Areas

1. NTDS.dit Database Analysis

The NTDS.dit file is the core Active Directory credential database containing all password hashes for domain accounts. Attackers commonly exfiltrate this file using tools like ntdsutil, secretsdump.py, or DCSync attacks via Mimikatz.

Detection indicators:

Event ID 4662: Access to directory service objects with replication permissions
Event ID 4742: Computer account modifications on domain controllers
Volume Shadow Copy creation on domain controllers (Event ID 8222)
Unusual ntdsutil.exe or vssadmin.exe execution
Replication traffic from non-DC sources (DCSync detection)

2. Kerberos Attack Detection

Golden Ticket indicators:

TGT tickets with abnormally long lifetimes (default is 10 hours)
Event ID 4769 with encryption type 0x17 (RC4) instead of AES
TGT issued without corresponding Event ID 4768 (AS-REQ)
Kerberos tickets referencing non-existent or disabled accounts

Silver Ticket indicators:

Service tickets without corresponding TGT requests
Event ID 4769 with unusual service names
Tickets with forged PAC data

Kerberoasting indicators:

High volume of Event ID 4769 for service accounts
RC4 encryption requests for accounts that support AES
Requests from workstations not normally accessing those services

3. Group Policy Abuse

GPO modifications granting new privileges (Event ID 5136)
Scheduled task deployment via GPO
Software installation policies added to domain
Login script modifications
Registry-based policy changes for persistence

4. Privileged Group Enumeration

Track modifications to these critical groups:

Domain Admins, Enterprise Admins, Schema Admins
Account Operators, Backup Operators
DnsAdmins (can execute arbitrary DLLs on DCs)
Group Policy Creator Owners
Protected Users group membership changes

5. Trust Relationship Analysis

New forest/domain trusts created (Event ID 4706)
SID History injection for privilege escalation
Trust ticket forgery indicators
Cross-domain authentication anomalies

Investigation Methodology

Phase 1: Scoping and Evidence Collection

1. Identify potentially compromised domain controllers
2. Collect Security, System, Directory Service event logs
3. Extract AD replication metadata using repadmin
4. Capture ntdsutil snapshots for offline analysis
5. Collect DNS server logs and zone transfer records
6. Export Group Policy Object configurations
7. Document current privileged group memberships

Phase 2: Authentication Log Analysis

1. Parse Event ID 4624/4625 for logon patterns
2. Identify pass-the-hash indicators (Event ID 4624 Type 3 with NTLM)
3. Analyze Event ID 4768/4769/4771 for Kerberos anomalies
4. Review Event ID 4776 for NTLM authentication failures
5. Cross-reference logon events with known compromised accounts
6. Map lateral movement paths through authentication chains

Phase 3: Persistence and Backdoor Detection

1. Enumerate AdminSDHolder ACL modifications
2. Check for SID History abuse on accounts
3. Verify krbtgt account password age
4. Audit DSRM password configuration
5. Check for skeleton key malware indicators
6. Review AD Certificate Services for rogue certificates
7. Validate DNS records for poisoning

Phase 4: Remediation Planning

1. Double-rotate krbtgt password (wait replication between rotations)
2. Reset all compromised account passwords
3. Remove unauthorized privileged group members
4. Revoke rogue certificates if AD CS compromised
5. Rebuild domain controllers from clean media if needed
6. Implement tiered administration model
7. Enable Protected Users group for privileged accounts

Critical Event IDs for AD Investigation

Event ID	Source	Description
4624	Security	Successful logon
4625	Security	Failed logon
4648	Security	Explicit credential logon
4662	Security	Operation on AD object
4768	Security	Kerberos TGT requested
4769	Security	Kerberos service ticket requested
4771	Security	Kerberos pre-authentication failed
4776	Security	NTLM credential validation
5136	Security	Directory object modified
5137	Security	Directory object created
4706	Security	Trust created
4707	Security	Trust removed
4742	Security	Computer account changed
8222	System	Shadow copy created

Tools for AD Investigation

Tool	Purpose
BloodHound	Attack path mapping and privilege escalation analysis
Pingcastle	AD security assessment and risk scoring
Purple Knight	AD vulnerability scanning by Semperis
ADRecon	Active Directory data gathering
Mimikatz	Credential extraction and Kerberos analysis
Impacket	DCSync detection and NTLM relay analysis
Velociraptor	Remote forensic artifact collection
Timeline Explorer	Event log timeline analysis

MITRE ATT&CK Mapping

Technique	ID	Relevance
DCSync	T1003.006	NTDS.dit credential extraction
Golden Ticket	T1558.001	Kerberos TGT forgery
Silver Ticket	T1558.002	Service ticket forgery
Kerberoasting	T1558.003	Service account hash extraction
Pass-the-Hash	T1550.002	NTLM hash reuse
Group Policy Modification	T1484.001	Persistence via GPO
Account Manipulation	T1098	Privileged group changes
SID-History Injection	T1134.005	Privilege escalation

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