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HTB Academy: Active Directory Enumeration & Attacks

Page 5 - Initial Enumeration of the Domain

Overview

Starting phase of Active Directory penetration testing against Inlanefreight domain. Beginning from an attack host placed inside the network without domain credentials.

Test Environment Setup

Client Configuration:

  • Custom pentest VM within internal network (calls back to jump host)
  • Windows host available for tool loading
  • Starting unauthenticated with standard domain user account available (htb-student)
  • Network range: 172.16.5.0/23
  • Grey box testing approach
  • Non-evasive testing

Key Objectives

  1. Enumerate internal network - identify hosts, services, attack vectors
  2. Document findings for later use
  3. Find domain user account or SYSTEM access on domain-joined host

Enumeration Methodology

1. Passive Network Analysis

Wireshark Traffic Capture

Technique: Monitor network traffic to identify hosts and services

# Start Wireshark GUI
sudo -E wireshark

# Command line alternative
sudo tcpdump -i ens224

Key Findings:

  • ARP packets reveal active hosts: 172.16.5.5, 172.16.5.25, 172.16.5.50, 172.16.5.100, 172.16.5.125
  • MDNS queries reveal hostnames: ACADEMY-EA-WEB01.local

Responder Passive Analysis

Technique: Analyze LLMNR, NBT-NS, and MDNS traffic passively

# Passive analysis mode (no poisoning)
sudo responder -I ens224 -A

Benefits:

  • Non-intrusive reconnaissance
  • Discovers additional hosts not seen in basic scans
  • Identifies naming conventions and network structure

2. Active Host Discovery

FPing Network Sweep

Technique: ICMP sweep to identify live hosts

# Quick ICMP sweep with summary
fping -asgq 172.16.5.0/23

Example Output:

172.16.5.5
172.16.5.25
172.16.5.50
172.16.5.100
172.16.5.125
172.16.5.200
172.16.5.225
172.16.5.238
172.16.5.240

     510 targets
       9 alive
     501 unreachable

Flags Explained:

  • -a : Show targets that are alive
  • -s : Print stats at end of scan
  • -g : Generate target list from CIDR
  • -q : Quiet (don't show per-target results)

3. Service Enumeration

Nmap Comprehensive Scanning

Technique: Detailed service and version detection

# Aggressive scan against host list
sudo nmap -v -A -iL hosts.txt -oN /home/htb-student/Documents/host-enum

# Single host detailed scan
sudo nmap -A -v -Pn 172.16.5.5

# Network-wide scan with grepable output
sudo nmap -A -Pn -T5 -oG ./nmapOutput 172.16.5.0/23

Critical Service Discovery

Domain Controller (172.16.5.5) - ACADEMY-EA-DC01.INLANEFREIGHT.LOCAL:

PORT     STATE SERVICE       VERSION
53/tcp   open  domain        Simple DNS Plus
88/tcp   open  kerberos-sec  Microsoft Windows Kerberos
135/tcp  open  msrpc         Microsoft Windows RPC
139/tcp  open  netbios-ssn   Microsoft Windows netbios-ssn
389/tcp  open  ldap          Microsoft Windows Active Directory LDAP
445/tcp  open  microsoft-ds
464/tcp  open  kpasswd5
593/tcp  open  ncacn_http    Microsoft Windows RPC over HTTP 1.0
636/tcp  open  ssl/ldap      Microsoft Windows Active Directory LDAP
3268/tcp open  ldap          Microsoft Windows Active Directory LDAP
3269/tcp open  ssl/ldap      Microsoft Windows Active Directory LDAP
3389/tcp open  ms-wbt-server Microsoft Terminal Services

Legacy System (172.16.5.100) - Potential Quick Win:

PORT     STATE SERVICE      VERSION
80/tcp   open  http         Microsoft IIS httpd 7.5
135/tcp  open  msrpc        Microsoft Windows RPC
139/tcp  open  netbios-ssn  Microsoft Windows netbios-ssn
445/tcp  open  microsoft-ds Windows Server 2008 R2 Standard 7600
1433/tcp open  ms-sql-s     Microsoft SQL Server 2008 R2 10.50.1600.00

⚠️ Security Note: Legacy systems present high-value targets for exploits like EternalBlue, MS08-067. Always get client approval before exploiting to avoid system instability.

4. User Enumeration

Kerbrute Installation & Setup

Technique: Kerberos pre-authentication username enumeration

# Clone repository
sudo git clone https://github.com/ropnop/kerbrute.git
cd kerbrute

# View compile options
make help

# Compile for all platforms
sudo make all

# Install binary
sudo mv kerbrute_linux_amd64 /usr/local/bin/kerbrute

Username Enumeration Attack

Technique: Leverage Kerberos pre-auth failures (often doesn't trigger alerts)

# Enumerate users against DC with wordlist
kerbrute userenum -d INLANEFREIGHT.LOCAL --dc 172.16.5.5 jsmith.txt -o valid_ad_users

Example Results:

[+] VALID USERNAME:       jjones@INLANEFREIGHT.LOCAL
[+] VALID USERNAME:       sbrown@INLANEFREIGHT.LOCAL  
[+] VALID USERNAME:       tjohnson@INLANEFREIGHT.LOCAL
[+] VALID USERNAME:       evalentin@INLANEFREIGHT.LOCAL
[+] VALID USERNAME:       sgage@INLANEFREIGHT.LOCAL
[+] VALID USERNAME:       jshay@INLANEFREIGHT.LOCAL
[+] VALID USERNAME:       jhermann@INLANEFREIGHT.LOCAL
[+] VALID USERNAME:       whouse@INLANEFREIGHT.LOCAL
[+] VALID USERNAME:       emercer@INLANEFREIGHT.LOCAL
[+] VALID USERNAME:       wshepherd@INLANEFREIGHT.LOCAL

Done! Tested 48705 usernames (56 valid) in 9.940 seconds

Benefits of Kerbrute:

  • ✅ Stealthy (pre-auth failures often don't log)
  • ✅ Fast (thousands of usernames in seconds)
  • ✅ Builds target list for password spraying
  • ⚠️ Caution: Can cause account lockouts if not careful

Key Data Points to Document

Data Point Description Use Cases
AD Users Valid user accounts discovered Password spraying, targeted attacks
AD Computers Domain Controllers, file servers, SQL servers, web servers, Exchange Service enumeration, lateral movement
Key Services Kerberos, NetBIOS, LDAP, DNS Protocol-specific attacks
Vulnerable Hosts Legacy systems, unpatched services Quick wins, privilege escalation

Paths to Domain Access

SYSTEM-Level Access Benefits

Gaining NT AUTHORITY\SYSTEM on domain-joined host provides:

  • Domain enumeration capabilities (computer account impersonation)
  • Kerberoasting/ASREPRoasting attacks
  • Net-NTLMv2 hash gathering with Inveigh
  • SMB relay attacks
  • Token impersonation for privileged accounts
  • ACL attacks

Common SYSTEM Access Methods

  1. Remote exploits: MS08-067, EternalBlue, BlueKeep
  2. Service abuse: SYSTEM services + SeImpersonate (Juicy Potato)
  3. Local privilege escalation: Windows Task Scheduler 0-day
  4. Local admin + Psexec: Launch SYSTEM cmd window

Scanning Best Practices

Operational Security Considerations

  • Evasive vs Non-evasive: Understand engagement rules
  • Network impact: Some scans can destabilize systems
  • Industrial environments: Be cautious with sensors/controllers
  • Documentation: Always use -oA flag for multiple output formats

Recommended Scan Approach

  1. Start passive: Wireshark, Responder analysis
  2. Light active: fping, basic port scans
  3. Targeted enumeration: Focus on discovered services
  4. Deep dive: Service-specific enumeration tools

Lab Questions & Solutions

Question 1: CommonName of host 172.16.5.5

Task: Find the commonName in SSL certificate

Solution:

# SSH to attack host
ssh htb-student@10.129.226.51
# Password: HTB_@cademy_stdnt!

# Scan target host
sudo nmap -A -v -Pn 172.16.5.5

Answer: ACADEMY-EA-DC01.INLANEFREIGHT.LOCAL

Location: Found in SSL-Cert details under port 3389 (RDP)

Question 2: Host running Microsoft SQL Server 2019 15.00.2000.00

Task: Find IP address of host running specific SQL Server version

Solution:

# Network-wide scan with grepable output
sudo nmap -A -Pn -T5 -oG ./nmapOutput 172.16.5.0/23

# Extract SQL Server hosts
awk '/1433\/open/ {print $2}' nmapOutput

# Alternative: grep for SQL Server version
grep "Microsoft SQL Server 2019 15.00.2000.00" nmapOutput

Answer: 172.16.5.130

Location: Found on port 1433 during service detection

Key Takeaways

  1. Methodical approach: Passive → Active → Targeted enumeration
  2. Documentation crucial: Save all scan outputs for later analysis
  3. Multiple tools: Different tools reveal different information
  4. Legacy systems: High-value targets but require caution
  5. User enumeration: Critical for subsequent password attacks
  6. Service focus: Target AD-specific protocols (LDAP, Kerberos, DNS)

Next Steps

  • Password spraying against enumerated users
  • Service-specific enumeration (SMB, LDAP, etc.)
  • Vulnerability assessment of discovered hosts
  • Search for foothold opportunities

Useful Wordlists

  • Usernames: jsmith.txt, jsmith2.txt (from Insidetrust repository)
  • Passwords: Common corporate passwords, season+year patterns
  • Subdomain enumeration: SecLists various wordlists

Command Reference

Network Discovery

# Passive analysis
sudo wireshark
sudo tcpdump -i ens224
sudo responder -I ens224 -A

# Active discovery  
fping -asgq 172.16.5.0/23
sudo nmap -sn 172.16.5.0/23

# Service enumeration
sudo nmap -A -v -Pn TARGET
sudo nmap -A -Pn -T5 -oA scan_results 172.16.5.0/23

User Enumeration

# Kerbrute setup
git clone https://github.com/ropnop/kerbrute.git
make all
sudo mv kerbrute_linux_amd64 /usr/local/bin/kerbrute

# Username enumeration
kerbrute userenum -d DOMAIN --dc DC_IP wordlist.txt -o valid_users

Data Processing

# Extract specific services
awk '/PORT_NUMBER\/open/ {print $2}' nmap_output.gnmap
grep "SERVICE_NAME" nmap_output

# Format for further tools
cat valid_users | cut -d@ -f1 > usernames.txt

This methodology provides a systematic approach to initial AD enumeration, balancing thoroughness with operational security considerations.