Performing Kerberoasting Attack

Overview

Kerberoasting is a post-exploitation technique that targets service accounts in Active Directory by requesting Kerberos TGS (Ticket Granting Service) tickets for accounts with Service Principal Names (SPNs) set. These tickets are encrypted with the service account's NTLM hash, allowing offline brute-force cracking without generating failed login events. It is one of the most common privilege escalation paths in AD environments because any domain user can request TGS tickets.

MITRE ATT&CK Mapping

• T1558.003 - Steal or Forge Kerberos Tickets: Kerberoasting
• T1087.002 - Account Discovery: Domain Account
• T1069.002 - Permission Groups Discovery: Domain Groups

Implementation Steps

Phase 1: SPN Enumeration

1. Enumerate accounts with SPNs using LDAP queries
2. Filter for user accounts (not computer accounts)
3. Identify accounts with elevated privileges (adminCount=1)
4. Prioritize accounts with weak password policies

Phase 2: TGS Ticket Request

1. Request TGS tickets for identified SPN accounts
2. Extract ticket data in crackable format (hashcat/john compatible)
3. Ensure RC4 encryption is requested when possible (easier to crack)
4. Document all requested tickets

Phase 3: Offline Cracking

1. Use hashcat mode 13100 (Kerberos 5 TGS-REP etype 23) for RC4 tickets
2. Use hashcat mode 19700 (Kerberos 5 TGS-REP etype 17) for AES-128
3. Use hashcat mode 19800 (Kerberos 5 TGS-REP etype 18) for AES-256
4. Apply targeted wordlists and rules based on password policy

Phase 4: Credential Validation

1. Validate cracked credentials against domain
2. Assess access level of compromised accounts
3. Map accounts to BloodHound attack paths
4. Document for engagement report

Tools and Resources

Detection Indicators

• Event ID 4769: Kerberos Service Ticket Request with RC4 encryption (0x17)
• Anomalous TGS requests from a single account in short timeframe
• TGS requests for services the user normally does not access
• Honeypot SPN accounts with alerting on ticket requests

Validation Criteria

• [ ] SPN accounts enumerated and documented
• [ ] TGS tickets extracted in crackable format
• [ ] Offline cracking attempted with appropriate wordlists
• [ ] Cracked credentials validated
• [ ] Access level of compromised accounts assessed