Internal Network Penetration Testing Methodology

A structured, risk-focused approach for evaluating internal corporate security, lateral movement potential, and privilege escalation paths within enterprise networks.

1. Objective & Scope

An internal network penetration test simulates an attacker who already has a foothold inside the environment, whether through phishing, compromised credentials, malware, or an insider threat.

The primary goals are:

  • Assessing lateral movement viability
  • Evaluating privilege escalation paths to high-value roles
  • Mapping Active Directory attack paths
  • Identifying segmentation and access control breakdowns
  • Detecting insecure configurations and vulnerabilities
  • Understanding the “blast radius” of an internal compromise

Scope may include:

  • Workstations, servers, and Domain Controllers
  • Internal web applications and APIs
  • Shared file servers and databases
  • Authentication systems and SSO flows
  • Hybrid/on-prem/cloud-connected resources
  • OT/ICS assets (if in scope)

2. Assumptions & Constraints

Internal testing relies on clearly defined rules of engagement, which typically include:

  • A starting foothold such as a workstation, VPN, or wired connection
  • No destructive testing or service disruption
  • No altering production configurations beyond safe PoC steps
  • Privilege escalation allowed within ROE
  • Controlled password spraying to avoid lockouts
  • Lateral movement permitted under defined restrictions
  • Kerberoasting and AS-REP roasting allowed
  • Token theft and impersonation allowed depending on policy

These boundaries ensure realistic but safe operator behavior.

3. Operational Philosophy

My internal testing strategy emphasizes:

  • Stealth and precision — avoid unnecessary noise, focus on signal.
  • Credentials over exploits — real attacks succeed through identity compromise.
  • Measured privilege escalation — escalate only when it yields meaningful access.
  • Attack path mapping — AD relationships matter more than raw vulnerabilities.
  • Demonstrating risk safely — clarity and controlled testing over aggression.

This mirrors realistic attacker behavior while maintaining professional safety standards.

4. High-Level Workflow

Phase 1 — Environmental Awareness & Initial Enumeration

  • Identify host context, privileges, and domain membership
  • Enumerate local users, privileges, and logged-in sessions
  • Discover local networks, subnets, and reachable hosts
  • Identify Domain Controllers and authentication sources
  • Collect technical fingerprints and system metadata

Objective: understand the position and value of the initial foothold.

Phase 2 — Active Directory Enumeration

  • Enumerate domain users, groups, OUs, and permissions
  • Identify privileged accounts and administrative roles
  • Analyze ACLs for privilege abuse opportunities
  • Identify delegation, unconstrained and constrained Kerberos scenarios
  • Map AD relationships with graph-based tooling

This phase reveals viable privilege escalation paths and identity weaknesses.

Phase 3 — Credential Gathering & Authentication Weaknesses

Credentials are the core of internal compromise. Techniques include:

  • Safe LSASS dumping (token extraction or nanodump)
  • DPAPI secret retrieval
  • Harvesting credentials from scripts, configs, services, and logs
  • Capturing NTLM authentication through relays if permitted
  • Kerberoasting and AS-REP roasting
  • Password spraying with lockout-aware throttling
  • Exploiting credential reuse or shared local admin passwords

This phase is about obtaining new identities to expand reach.

Phase 4 — Lateral Movement

  • SMB-based command execution
  • WinRM and remote PowerShell
  • WMI-based movement
  • DCOM invocation
  • RDP where permitted

Lateral movement is targeted and guided by AD attack path analysis.

Phase 5 — Privilege Escalation

  • Abusing weak ACLs and misconfigurations
  • Escalation via vulnerable services or scheduled tasks
  • Service account misconfigurations and path hijacking
  • Token impersonation and SeImpersonate privilege abuse
  • Following AD-derived escalation paths toward high-value roles

The goal is to understand the feasibility of reaching privileged identities such as Domain Admin.

Phase 6 — Post-Exploitation & Impact Analysis

  • Validate control over high-value systems
  • Enumerate sensitive data access where permitted
  • Assess persistence opportunities
  • Evaluate segmentation breakdowns
  • Review monitoring and detection visibility

This phase translates technical compromise into business-level impact.

Phase 7 — Cleanup

  • Remove tools, binaries, and logs from systems
  • Restore modified services or configurations
  • Validate no artifacts remain in memory or on disk

Cleanup preserves integrity and ensures a safe return to normal operations.

5. Tooling & Tradecraft

Representative tools used during internal engagements include:

  • Enumeration & AD Mapping: BloodHound, NetExec, PowerView, LDAP queries, custom scripts
  • Credential Gathering: Nanodump, DPAPI tools, token manipulation utilities
  • Lateral Movement: Impacket suite, WinRM, WMIexec, DCOM-based techniques
  • Privilege Escalation: ACL exploitation, service misconfig tools, identity-based escalation patterns
  • OPSEC: targeted enumeration, minimized scanning, reduced authentication noise

The emphasis is on controlled movement, impact demonstration, and clarity—not indiscriminate scanning.

6. Deliverables

A complete internal penetration test includes:

  • Executive summary for business-level clarity
  • Attack path diagrams and AD relationship mapping
  • Technical findings with reproduction steps
  • Credential and identity abuse analysis
  • Lateral movement and escalation path documentation
  • Impact analysis outlining real-world consequences
  • A prioritized remediation plan
  • Hardening guidance for AD, identity, endpoint, and segmentation models

The goal is to provide organizations with clear, actionable insights into their internal security posture and identity risks.