Internal LAN Security Audits

What is an Internal LAN Security Audit?

An internal LAN security audit is a structured assessment of your organisation’s on‑premises network to identify vulnerabilities, misconfigurations, and threats that reside inside the perimeter. Unlike external penetration tests that emulate outside attackers, an internal audit assumes the vantage‑point of an authenticated user or compromised device. The goal is to detect issues before a malicious insider or lateral‑moving attacker does.

This guide covers every aspect you need to launch or improve your own audit. Throughout, we link to OSI.Security resources for deeper technical dives.

Audit Process Overview

1. Scoping & Asset Discovery – Map subnets, devices, and trust relationships.
2. Baseline Configuration Review – Compare devices against secure configuration benchmarks.
3. Credential Hygiene Analysis – Identify weak, reused, or default passwords.
4. Privilege Escalation Testing – Attempt to move from standard user to admin.
5. Data Exfiltration Simulation – Verify egress controls and DLP effectiveness.
6. Reporting & Remediation Planning – Prioritise findings by risk and business impact.

Open‑Source & Commercial Tools

• Nmap – Port scanning and host discovery
• BloodHound – Attack path mapping in Active Directory
• PowerShell’s Get-AD* Cmdlets – Quick AD misconfiguration checks
• Azure AD Assessments (Microsoft Graph + Az PowerShell)
• Responder & Inveigh – LLMNR/NBNS spoofing & credential capture
• Samba’s enum4linux-ng – SMB share & user enumeration
• Wireshark – Traffic inspection for rogue AP detection
• Commercial Suites: Tenable Nessus, Rapid7 InsightVM, PlexTrac for reporting

Azure & On‑Prem Active Directory Auditing

Hybrid identity means your audit can’t stop at the server‑room door. Key focus areas:

Azure AD

• Conditional Access Policies – Look for blanket “All Users” rules.
• App Registrations – Review OAuth2Permissions and consented scopes.
• Privileged Identity Management (PIM) – Validate eligible role expirations.
• Sign‑in Logs – Hunt for impossible travel anomalies.

On‑Prem AD

• AD DS Baselines – CIS or Microsoft Security Baseline comparisons.
• GPO Review – Detect broad SeDebugPrivilege assignments.
• AdminSDHolder & SDProp – Ensure protected groups remain locked down.

SMB, Default Credentials, & Lateral Movement

Server Message Block (SMB) remains a favourite avenue for attackers to pivot inside networks:

• Enumerate shares with enum4linux-ng or smbmap.
• Scan for ADMIN$ access using known credentials.
• Check devices for factory credentials—e.g., admin:password—especially in legacy NAS or printer appliances.
• Disable SMBv1 and enforce SMB signing to mitigate relay attacks.

Misconfigured Wi‑Fi APs & Rogue Clients

Even wired networks rely on radio waves. Common pain points:

• Pre‑Shared Keys (PSK) posted on walls or shared with contractors.
• Rogue Access Points splicing directly into switch ports.
• Evil‑Twin Attacks luring clients to malicious SSIDs.
• 802.1X Supplicants silently failing over to insecure open SSIDs.

Audit Tip: Use spectrum analysis and periodic wireless sweeps. Validate AP firmware and disable WPS.

Modern Internal Threats

Today’s attackers combine cloud APIs, commodity malware, and living‑off‑the‑land binaries:

• Credential Theft Malware (Mimikatz, LaZagne) harvesting NTLM hashes.
• Shadow IT Containers running unsecured services on developer laptops.
• Bring‑Your‑Own‑AI tools uploading sensitive prompts to external LLMs.
• Misconfigured Zero‑Trust Agents creating split‑tunnel data leaks.

Best Practices & Hardening Checklist

• Enforce unique, random local admin passwords (LAPS / Intune LAPS).
• Implement network segmentation—block SMB between workstations.
• Deploy endpoint detection & response (EDR) with lateral movement rules.
• Review privileges via Get-LocalGroupMember and BloodHound queries monthly.
• Patch firmware: switches, APs, printers—often overlooked.
• Log everything centrally (Syslog, Azure Sentinel) with >12‑month retention.
• Conduct follow‑up audits after significant infrastructure changes.

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Learn More

Need professional assistance? Visit OSI.Security for expert internal audit and penetration testing services.