A Guide to a Real Computer Network Security Audit in 2025
In 2025, an estimated 68% of successful network intrusions will begin with stolen NTLM hashes or Kerberos tickets, bypassing traditional perimeter defenses entirely. Conducting a thorough computer network security audit is no longer optional; it is the essential practice for finding and fixing the modern attack paths that adversaries now exploit. This guide provides a direct, actionable roadmap for a 2025-ready audit that uncovers real-world risks, prepares you for complex compliance demands, and delivers a clear remediation plan.
Table of Contents
- What Is a Computer Network Security Audit in 2025?
- Pre-Audit: Scope, Asset Inventory & Risk Profiling
- External Reconnaissance & Vulnerability Scanning
- Internal Network Discovery & Lateral Movement Testing
- Authentication, Privileged Access & Zero-Trust Verification
- Network Segmentation, Encryption & Data Flow Analysis
- Logging, Monitoring & EDR/SIEM Effectiveness Check
- Remediation Roadmap & Continuous Audit Automation
What Is a Computer Network Security Audit in 2025?
A modern network security audit is a deep, adversarial evaluation of your defenses, policies, and response capabilities against 2025-level threats like AI-assisted recon, token theft, and EDR evasion. Unlike a simple scan, its goal is to think like an attacker to validate that security controls are not just present but are actually working as intended to stop sophisticated, multi-stage attacks before they achieve their objectives.
From the Trenches: During a recent audit kickoff, the client insisted their "next-gen EDR" would block everything. We used a simple living-off-the-land binary (LOLBin), `wmic.exe`, to execute a command that the EDR completely ignored because the process was signed by Microsoft. This 30-second demonstration immediately shifted the audit's focus from just checking configurations to testing for realistic EDR evasion techniques that attackers use daily.
1. Define Scope: Explicitly document all IP ranges, cloud environments, and critical applications that are in-scope for the audit. 2. Identify Threat Actors: Profile your likely adversaries. Are they financially motivated ransomware groups or nation-state actors targeting intellectual property? 3. Review Existing Policies: Collect and analyze current security policies, network diagrams, and previous audit reports to establish a baseline. 4. Set Success Criteria: Define what a successful audit looks like. Is it achieving a specific compliance goal (e.g., prepare for your first SOC 2 audit) or identifying all critical paths to sensitive data? 5. Establish Communication Rules: Set up a secure communication channel and define the rules of engagement, including testing windows and escalation contacts for critical findings.
Pre-Audit: Scope, Asset Inventory & Risk Profiling
A successful security audit starts with a solid plan, not a port scan. First, define exactly what you’re testing and why—are you focused on a specific subnet hosting critical applications, or is the entire cloud environment in-scope? The next critical step is building a comprehensive inventory of every single network device and application; you cannot protect what you don’t know you have.
From the Trenches: A client swore their production environment was completely isolated. We found a forgotten developer VPN profile that granted direct access from the internet, completely bypassing their new firewall. The asset was not in their inventory, so it was never patched or monitored. An attacker using AI-assisted reconnaissance could have found this in hours. The discovery immediately demonstrated the critical need for automated, continuous asset discovery.
Open-Source Asset Discovery Tool Comparison
| Tool | Primary Function | Key Feature for Audits | Best For |
|---|---|---|---|
| Nmap | Network Discovery & Port Scanning | Provides a raw list of live hosts, open ports, and running services. The ground truth of what’s on your network. | Getting a quick, foundational list of all active IP addresses and services to start your inventory. |
| Zabbix | Network Monitoring | Its auto-discovery feature can find and map network devices, servers, and services for ongoing monitoring. | Organizations needing a continuous inventory that also monitors the health and performance of those assets. |
| Snipe-IT | IT Asset Management (ITAM) | Creates a centralized, auditable record of all IT assets, including ownership and physical location. | Building a formal, managed inventory of both hardware and software assets that auditors will love. |
| RustScan | Fast Port Scanning | Incredibly fast port discovery that can be piped into Nmap for service enumeration, speeding up initial recon. | Quickly mapping the attack surface of large IP ranges to identify live hosts for deeper analysis. |
1. Automate Discovery: Use tools like Nmap or Zabbix to perform an initial sweep of all in-scope network segments to identify active hosts and services. 2. Correlate with Existing Records: Compare the automated discovery results against your CMDB or tools like Snipe-IT to identify undocumented or “shadow IT” assets. 3. Assign Asset Ownership: Ensure every discovered asset (servers, switches, applications) has a clearly documented business and technical owner. 4. Classify Data: Tag assets based on the sensitivity of the data they process or store (e.g., Public, Confidential, Restricted). 5. Profile Risks: For each asset, perform a high-level risk assessment. What is the business impact if it’s compromised? This helps prioritize later testing.
External Reconnaissance & Vulnerability Scanning
To build a solid defense, you must first think like an attacker. This means stepping outside your network and looking back at it from the public internet, hunting for any crack an adversary could slip through. We map out every public-facing asset—open ports, forgotten subdomains, and active services—that could be an entry point for threats like supply-chain implants or AI-assisted reconnaissance. Tools like Nmap or the incredibly fast RustScan are perfect for discovering what a real-world attacker would see first.
From the Trenches: During an external scan, we found a client's CI/CD server was accidentally exposed to the internet on a non-standard port. An AI-powered subdomain scanner would have flagged it instantly. The server contained build secrets that would have given an attacker access to their entire production cloud environment. We found it in the first hour of the audit, highlighting how quickly a simple misconfiguration can become a critical risk in the face of modern scanning tools.
1. Perform Full Port Scans: Use RustScan and Nmap to scan all 65,535 TCP and top UDP ports on your public IP ranges to find all open services. 2. Enumerate Subdomains: Use open-source tools to discover all subdomains, including those for development and testing that may be forgotten but are still live. 3. Identify Web Technologies: Fingerprint the technologies running on discovered web servers to identify potentially vulnerable software versions. 4. Search for Exposed Credentials: Run TruffleHog against public code repositories (e.g., GitHub) to find any leaked API keys or credentials associated with your organization. 5. Review DNS Records: Analyze public DNS records (MX, TXT, SPF) for misconfigurations that could be exploited for phishing or spoofing attacks. 6. Check for Known Vulnerabilities: Run an unauthenticated vulnerability scan against all discovered external services to identify low-hanging fruit like outdated software.
Internal Network Discovery & Lateral Movement Testing
Assume an attacker is already inside. This audit phase simulates their next moves, testing how easily they could jump from a compromised laptop to a domain controller. We stress-test defenses against modern threats like the NTLM relay revival, token theft, and the use of living-off-the-land binaries (LOLBins). The goal is to find and shut down these internal attack paths before an adversary can exploit them.
From the Trenches: On a recent audit, we used [BloodHound Sharp](https://github.com/BloodHoundAD/SharpHound) and found a direct, three-hop path from a marketing intern’s account to Domain Admin. The path existed because of nested group memberships and a forgotten GPO permission. It took the tool minutes to find a vulnerability that had likely existed for years, completely invisible to their monitoring tools. This discovery shifted their entire remediation priority list overnight.
Lateral Movement Toolset
| Tool | Attack Tested | Objective |
|---|---|---|
| BloodHound Sharp | Privilege Escalation Paths | Visualize Active Directory permissions to find the shortest path from a low-privilege account to Domain Admin. |
| CrackMapExec2 | Credential Stuffing / NTLM Relay | Spray passwords against accounts and test for systems vulnerable to NTLM relay attacks. |
| Impacket Scripts | Kerberoasting / Pass-the-Hash | Identify and attempt to crack service account passwords or reuse stolen hashes to access other systems. |
| TruffleHog | Exposed Secret Discovery | Scan internal file shares, wikis, and code repos for hardcoded passwords, API keys, and tokens. |
1. Map Attack Paths: Use BloodHound Sharp to ingest Active Directory data and visualize privilege escalation routes to high-value targets. 2. Test for Weak Credentials: Employ CrackMapExec to check for weak passwords and identify systems vulnerable to NTLM relaying. 3. Hunt for Kerberoastable Accounts: Use Impacket tools to find service accounts with weak encryption that are susceptible to offline password cracking. 4. Scan for Hardcoded Secrets: Deploy TruffleHog to scan internal file shares, wikis, and code repositories for exposed credentials and API keys. 5. Test Egress Filtering: From a simulated compromised host, attempt to connect to external C2 (Command and Control) servers to verify that network egress controls are effective.
Authentication, Privileged Access & Zero-Trust Verification
Identity is the new perimeter, making a rigorous access control audit non-negotiable. This goes beyond checking password policies and MFA enablement. We actively hunt for subtle but devastating risks like stolen access tokens, service accounts with excessive permissions, and hardcoded credentials in configuration files. The goal is to prove, not just assume, that the principle of least privilege is enforced everywhere and resilient against modern token theft and EDR evasion techniques.
From the Trenches: During an audit, we found a legacy service account with a non-expiring password. Privilege creep had given it a Kerberos Service Principal Name (SPN), making it vulnerable to a Kerberoasting attack. We cracked its weak password in under an hour. This one forgotten account gave us a direct line from a non-critical system to a database with sensitive PII, completely bypassing layers of other controls that were focused on user accounts.
1. Validate Account Lifecycles: Systematically review and confirm that all accounts—including service, vendor, and temporary accounts—are disabled immediately upon offboarding. 2. Hunt for Hardcoded Secrets: Run tools like TruffleHog against internal code repositories, config files, and CI/CD logs to find exposed API keys and database credentials. 3. Test MFA for Bypass Vulnerabilities: Actively test for MFA bypass methods like session token hijacking or consent phishing attacks, not just verifying that MFA is enabled. 4. Enforce True Least Privilege: Use BloodHound to visualize Active Directory permissions, identifying and eliminating excessive privileges accumulated over time. 5. Scrutinize Session and Token Policies: Review session timeout settings, token lifecycles, and refresh token policies to ensure stolen tokens have a limited window of utility. 6. Audit All Privileged Accounts: Review every account in privileged groups (e.g., Domain Admins, Enterprise Admins) and justify its membership based on a documented business need.
Network Segmentation, Encryption & Data Flow Analysis
A flat network is an attacker’s playground. Proper network segmentation and end-to-end encryption are your only effective defenses against lateral movement. This phase of the audit scrutinizes firewall rules, VLAN configurations, and cloud security group policies to ensure critical assets are isolated. We don’t just check that segmentation exists; we use tools like Wireshark to capture traffic and verify that sensitive data flowing between segments is actually encrypted, shutting down sniffing attacks.
From the Trenches: We audited a company with a perfectly isolated credit card processing environment. However, the firewall rule allowing log data out to their SIEM was misconfigured with an ‘any/any’ protocol. This tiny mistake created a covert channel an attacker could have used to exfiltrate data from their most secure zone, completely bypassing all other controls. It's a classic case of a simple oversight creating a massive risk.
Network Segmentation Scorecard
| Control | Not Implemented (0) | Partially Implemented (1) | Fully Implemented (2) |
|---|---|---|---|
| Prod/Dev/Test Separation | Flat network, all environments can communicate. | ACLs exist but are overly permissive. | Strict firewall rules deny all traffic by default. |
| Critical Asset Isolation | Domain controllers are on the same subnet as user workstations. | Critical assets are on a separate VLAN, but rules are loose. | Critical assets are in a secure enclave with explicit allow rules. |
| Encryption in Transit | Internal traffic is sent in cleartext. | Some traffic is encrypted, but legacy protocols (e.g., TLS 1.1) are allowed. | All sensitive traffic is forced over TLS 1.3. |
| Egress Filtering | All outbound traffic is allowed. | Outbound traffic is restricted by port, but not by destination IP. | Outbound traffic is denied by default; only approved destinations are allowed. |
1. Map Network Segments: Use network diagrams and firewall rulebases to create a visual map of all segments (production, dev, DMZ, corporate). 2. Dissect Firewall and ACL Rules: Scrutinize access control lists for overly permissive “any/any” rules that violate the principle of least privilege. 3. Verify Encryption in Transit: Use Wireshark to capture traffic between critical segments to confirm that sensitive data is being sent over encrypted protocols like TLS 1.3. 4. Test Segmentation Controls: Actively attempt to access resources in a high-security zone from a less-secure zone (e.g., guest WiFi) to confirm the connection is blocked. 5. Audit Cloud Security Groups: Review cloud security group rules to eliminate public exposure of services like RDP/SSH and ensure proper micro-segmentation.
Logging, Monitoring & EDR/SIEM Effectiveness Check
Your detection and response capabilities are only as good as the data you feed them. This phase tests the effectiveness of your logging, Endpoint Detection and Response (EDR), and Security Information and Event Management (SIEM) systems. We don’t just check if logs are being collected; we simulate real attacks, like using living-off-the-land binaries or known EDR evasion techniques, to see if an alert is actually generated and if it’s actionable.
From the Trenches: A client had a top-tier SIEM and EDR. We executed a simple PowerShell command to download a benign file from the internet, a classic first-stage attacker technique. The raw log was generated, but no alert was fired because the detection rule was tuned to look for more complex scripts, ignoring the basics. It proved that simply owning expensive tools means nothing without proper rule tuning and validation against common threats.
Essential Log Sources for a 2025 Audit
| Log Source | Critical Events to Monitor | Why It Matters |
|---|---|---|
| Domain Controllers | Event ID 4624 (Logon), 4768/4769 (Kerberos TGT/TGS), 4672 (Admin Logon) | Detects credential theft, pass-the-hash, and privilege escalation. |
| Firewall/VPC Flow Logs | Denied connections, unusual outbound traffic, connections to known bad IPs | Identifies reconnaissance, exfiltration attempts, and C2 communication. |
| Endpoint (EDR) | Process creation (esp. PowerShell, wmic), registry modifications, network connections | Detects malware execution, living-off-the-land techniques, and lateral movement. |
| Cloud Control Plane | Console logins, API key creation/usage, security group changes | Catches unauthorized access and misconfigurations in cloud environments. |
| DNS Server | Queries to unusual or long domain names, high-volume requests from one host | Identifies C2 communication channels using DNS tunneling. |
1. Verify Critical Log Sources: Confirm that essential sources like domain controllers, firewalls, and EDR agents are successfully sending logs to your SIEM. 2. Test Detection Rules: Execute controlled, non-destructive attack simulations (e.g., Atomic Red Team) to verify that your SIEM and EDR generate alerts as expected. 3. Check for EDR Evasion: Attempt common EDR bypass techniques to test the resilience and configuration of your endpoint security tools. 4. Review Alert Triage Procedures: Trace a simulated alert through your entire response process, from generation in the SIEM to ticket creation in a tool like TheHive. 5. Validate Log Integrity: Ensure that logs are protected from tampering and that retention policies meet compliance requirements. 6. Audit Network Intrusion Detection: Use an IDS like Suricata to monitor traffic and verify its ability to detect signatures of common network attacks.
Remediation Roadmap & Continuous Audit Automation
An audit’s findings are worthless until they are fixed. This final phase turns a list of vulnerabilities into a prioritized, actionable roadmap. We rank fixes based on risk, implementation effort, and business impact. When the average U.S. data breach is projected to cost $10.2 million in 2025, a clear, risk-based plan is essential for securing the resources needed to strengthen your defenses. This process also shifts your posture from a one-time audit to a cycle of continuous improvement—a core expectation for frameworks like SOC 2 and NIS2. For a complete guide, download our free Network Security Audit Checklist.
From the Trenches: We presented an audit finding—a critical NTLM relay vulnerability—to an executive board. Instead of just technical jargon, we showed a video of us taking over their domain controller in under five minutes. We explained it was a “medium-effort” fix with a “critical” risk rating. The CISO approved the emergency change control request on the spot. Visual, risk-based storytelling gets results when raw data doesn't.
2025 Compliance Checkpoint Matrix
| Audit Activity | NIS2 Directive | DORA | SEC Cybersecurity Rules | CMMC 2.0 |
|---|---|---|---|---|
| Network Segmentation Testing | Supports measures to prevent and minimize incident impact. | Core to ICT risk management and network partitioning. | Evidence of policies to manage network infrastructure risks. | Maps to Access Control (AC) domain controls for boundary definition. |
| Encryption Verification (TLS 1.3) | Supports data-in-transit security measures. | Fulfills requirements for securing data in transit. | Demonstrates diligence in protecting sensitive information. | Addresses SC.3.177, requiring FIPS-validated cryptography. |
| Firewall Rulebase Audit | Essential for implementing security measures for network systems. | Core part of testing security controls for network traffic. | Evidence of effective network access controls for risk disclosure. | Maps to AC and System and Communications Protection (SC) domains. |
| Lateral Movement Testing | Verifies effectiveness of incident handling and response capabilities. | Key for testing resilience against advanced threats. | Part of identifying and managing risks of unauthorized access. | Addresses controls related to detecting and containing intrusions. |
1. Prioritize with a Risk Matrix: Plot every finding on a matrix of “Likelihood of Exploit” vs. “Business Impact” to identify and tackle critical risks first. 2. Assign Clear Owners and Deadlines: Assign every task to a specific individual with a firm due date. Ambiguity kills remediation plans. 3. Frame Risks in Business Terms: Instead of “CVE-2025-XXXX,” explain the risk as: “This flaw could halt our payment processing system, stopping all revenue.” 4. Automate Baseline Scanning: Set up recurring, automated scans to check for new open ports, weak credentials, or configuration drift as an early warning system. 5. Integrate Findings into Workflows: Push security findings directly into developer tools like Jira, making security bug fixes a natural part of sprint planning. 6. Schedule Re-testing: Plan to have a third party (or separate internal team) re-test all critical and high-risk findings within 90 days to verify the fix is effective.
Network Security Audit FAQ
How long does a full computer network security audit take in 2025?
For a medium-sized organization, a comprehensive audit typically takes 3 to 6 weeks. This includes planning (1 week), active testing (2-3 weeks), and analysis/reporting (1-2 weeks). The exact duration depends on the network’s size and complexity.
Can AI fully automate a network security audit?
No. AI is powerful for automating tasks like reconnaissance and log analysis, but it cannot replace human expertise. A human auditor is still required for strategic thinking, testing business logic flaws, and interpreting findings within the context of business risk.
How much does a professional computer network security audit cost?
Costs vary widely based on scope, but for a mid-sized business in 2025, expect to invest between $15,000 and $50,000. The price depends on the number of IP addresses, applications, and the depth of testing required.
What’s the difference between a vulnerability scan and a full audit?
A vulnerability scan is an automated process that identifies known vulnerabilities (like missing patches). A full audit is a much deeper, human-led engagement that includes the scan but adds manual penetration testing, policy review, configuration analysis, and lateral movement testing to validate control effectiveness.
How often should organizations run a network security audit in 2025?
Best practice is to conduct a full, independent external audit annually. Internal audits and vulnerability scans should be performed more frequently, ideally on a quarterly or even monthly basis, especially for critical systems.
External auditor vs internal team—which is better?
Both are necessary. An internal team provides continuous monitoring and understands the business context. An external auditor provides an unbiased, fresh perspective and often brings specialized skills and experience with emerging threats that an internal team may not possess.
The insights from a properly executed computer network security audit are indispensable for building a resilient defense against modern threats. To ensure your process is as thorough as possible, download our free Network Security Audit Checklist. Start your next computer network security audit this week—your adversaries already did.