Network Penetration Testing Methodology

Network penetration testing is a systematic approach to evaluating the security of computer networks and systems. Unlike web application testing, network pentesting focuses on infrastructure vulnerabilities, network protocols, and system-level security weaknesses.

The Network Penetration Testing Process

A typical network pentest follows a structured methodology that mirrors how real attackers operate:

Network Security Layers

1. Pre-Engagement

  • Scoping: Define the test boundaries and objectives
  • Rules of Engagement: Establish what is and isn’t allowed
  • Legal Documentation: Ensure proper authorization is in place
  • Emergency Contacts: Plan for unexpected issues

2. Reconnaissance (Information Gathering)

Passive Reconnaissance

Gather information without directly interacting with the target:

# DNS enumeration
dig example.com
nslookup example.com

# WHOIS information
whois example.com

# Google dorking
site:example.com filetype:pdf

Active Reconnaissance

Directly probe the target systems:

# Network discovery
nmap -sn 192.168.1.0/24

# Port scanning
nmap -sS -sV -O -A target.com

# Service enumeration
nmap -sC -sV -p- target.com

3. Scanning and Enumeration

Network Mapping

  • Identify live hosts and network topology
  • Discover open ports and running services
  • Fingerprint operating systems and applications
# Comprehensive scan
nmap -sS -sV -sC -O -A --script=vuln target.com

# UDP scan (slower but important)
nmap -sU --top-ports 1000 target.com

# Aggressive service detection
nmap -sV --version-intensity 9 target.com

Service-Specific Enumeration

SSH (Port 22)

# SSH version detection
ssh -V target.com

# Test for weak algorithms
ssh-audit target.com

HTTP/HTTPS (Ports 80/443)

# Directory discovery
gobuster dir -u http://target.com -w /usr/share/wordlists/dirbuster/directory-list-2.3-medium.txt

# Technology fingerprinting
whatweb target.com

SMB (Ports 139/445)

# SMB enumeration
enum4linux target.com
smbclient -L //target.com
smbmap -H target.com

4. Vulnerability Assessment

Automated Vulnerability Scanning

# Nessus command line
/opt/nessus/bin/nessuscli scan --targets target.com --policy "Basic Network Scan"

# OpenVAS
openvas-cli -T target.com

# Nikto for web services
nikto -h http://target.com

Manual Vulnerability Analysis

  • Analyze service versions against CVE databases
  • Look for misconfigurations
  • Identify weak authentication mechanisms
  • Check for default credentials

5. Exploitation

Common Attack Vectors

Unpatched Services

# Search for exploits
searchsploit service_name version

# Metasploit usage
msfconsole
use exploit/windows/smb/ms17_010_eternalblue
set RHOSTS target.com
exploit

Weak Passwords

# SSH brute force
hydra -l admin -P /usr/share/wordlists/rockyou.txt ssh://target.com

# SMB password spraying
crackmapexec smb target.com -u users.txt -p passwords.txt

Social Engineering

  • Phishing campaigns
  • Physical security bypass
  • Phone-based attacks (vishing)

6. Post-Exploitation

Maintaining Access

  • Install persistent backdoors
  • Create additional user accounts
  • Schedule recurring access methods

Privilege Escalation

# Linux privilege escalation
./linpeas.sh
sudo -l
find / -perm -4000 2>/dev/null

# Windows privilege escalation
whoami /priv
.\winPEAS.exe

Lateral Movement

  • Use compromised credentials on other systems
  • Exploit trust relationships
  • Pivot through compromised hosts

Data Exfiltration

  • Identify sensitive data
  • Document findings without actually stealing data
  • Demonstrate potential impact

Essential Tools for Network Penetration Testing

Reconnaissance

  • Nmap: Network discovery and port scanning
  • Masscan: Fast port scanner
  • Zmap: Internet-wide network scanner
  • DNSrecon: DNS enumeration

Vulnerability Assessment

  • Nessus: Commercial vulnerability scanner
  • OpenVAS: Open-source vulnerability scanner
  • Nuclei: Fast vulnerability scanner

Exploitation

  • Metasploit: Exploitation framework
  • ExploitDB: Vulnerability and exploit database
  • Empire/Covenant: Post-exploitation frameworks

Post-Exploitation

  • Mimikatz: Windows credential extraction
  • BloodHound: Active Directory reconnaissance
  • LinPEAS/WinPEAS: Privilege escalation enumeration

Best Practices

  1. Document Everything: Keep detailed logs of all activities
  2. Stay Within Scope: Never test systems outside the agreed scope
  3. Minimize Impact: Avoid causing system disruptions
  4. Test Incrementally: Verify each step before proceeding
  5. Communicate Issues: Report critical findings immediately
  6. Clean Up: Remove any tools or changes made during testing
  • Always get written authorization before conducting any penetration test
  • Respect privacy: Don’t access personal or sensitive data unnecessarily
  • Follow responsible disclosure: Report vulnerabilities to the appropriate parties
  • Maintain confidentiality: Protect client information and findings

Conclusion

Network penetration testing is a complex discipline that requires technical expertise, methodical approach, and strong ethical guidelines. By following established methodologies and using appropriate tools, security professionals can help organizations identify and remediate network security weaknesses before they’re exploited by malicious actors.

The key to successful network penetration testing is combining automated tools with manual analysis and creative thinking to uncover vulnerabilities that automated scans might miss.

Disclaimer: This content is for educational and authorized testing purposes only. Always ensure you have explicit written permission before testing any network or system.