Performing Kerberoasting Attack

Performing Kerberoasting Attack

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

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.

When to Use

• When conducting security assessments that involve performing kerberoasting attack
• 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

Most Often Missed & How to Confirm

• Force RC4 (etype 23, 0x17) when possible — Rubeus.exe kerberoast /tgtdeleg or GetUserSPNs.py -request yields $krb5tgs$23$ hashes (hashcat 13100) that crack far faster than AES. If accounts are AES-only you'll see $krb5tgs$18$/$17$ (modes 19800/19700); don't skip those, just expect slower cracking.
• Targeted/high-value roasting is missed when operators bulk-roast everything: prioritize adminCount=1 SPN accounts and known high-priv SPNs (MSSQLSvc, HTTP, CIFS) — Rubeus.exe kerberoast /user:svc_sql /nowrap or GetUserSPNs -request-user.
• AS-REP roasting is the companion technique constantly forgotten: enumerate DONT_REQ_PREAUTH accounts and roast them — Rubeus.exe asreproast /format:hashcat ($krb5asrep$23$, hashcat 18200). A "no kerberoastable accounts" result doesn't mean no offline-crackable hashes exist.
• /tgtdeleg avoids requesting RC4 downgrade noise on hardened domains; default roasts can trip Event 4769 RC4 alerts.
• Positive signal: a $krb5tgs$ (or $krb5asrep$) hash extracted AND hashcat returns a plaintext (Status: Cracked), which then authenticates — crackmapexec smb <dc> -u <svc> -p '<cracked>'.
• Don't conclude "not kerberoastable" until: (1) SPN enumeration ran authenticated (any domain user can, but a failed bind returns empty), (2) both RC4 and AES tickets were requested, (3) AS-REP roast was also attempted, (4) honeypot/decoy SPNs were filtered out, and (5) extracted hashes ran against a real wordlist+rules (rockyou + best64) before calling it uncrackable.

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

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

Workflow

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