Every organization that connects systems to a network is exposed to risk. The question is not whether vulnerabilities exist, but how many, how severe, and whether anyone is actively looking for them. A network security audit is the structured process of answering those questions with precision, evidence, and actionable findings.
This guide breaks down the full audit lifecycle, from scoping and reconnaissance through reporting, using the tools and techniques that security professionals actually rely on in the field.
A network security audit is a systematic, technical evaluation of an organization's network infrastructure to identify vulnerabilities, misconfigurations, policy violations, and exposure to threats. It examines firewalls, routers, switches, endpoints, authentication systems, access controls, and traffic flows to produce a clear picture of the network's security posture.
Unlike a penetration test, which attempts to actively exploit weaknesses, an audit typically combines automated scanning, manual configuration review, policy analysis, and traffic inspection to document risk without necessarily weaponizing it. That said, many engagements blend both disciplines, and the line between audit and pentest is often deliberately blurred when the goal is maximum coverage.
Network security audits are conducted to satisfy compliance requirements such as PCI DSS, ISO 27001, HIPAA, and SOC 2, but compliance is a floor, not a ceiling. Organizations that audit only to check a regulatory box consistently miss the real-world attack paths that threat actors use.
Attackers do not need zero-days to compromise most enterprise networks. Unpatched services, overly permissive firewall rules, default credentials, and flat network architecture give them everything they need. A properly scoped audit surfaces these issues before someone with malicious intent does.
The business case is straightforward: the average cost of a data breach continues to rise year over year, and the majority of breaches involve known, preventable vulnerabilities. If your organization has not had a formal network audit in the past twelve months, you are operating with incomplete knowledge of your own attack surface. Redfox Cybersecurity's network security services are built around closing exactly that gap.
Every audit begins with a clearly documented scope. Without it, assessments drift, important assets get missed, and findings lack the context needed to prioritize remediation.
Key scoping questions:
Document all of this in a Rules of Engagement (RoE) document that is signed by both parties before any technical work begins. The RoE should include emergency contacts, escalation procedures, and explicit written authorization to test. This protects the audit team and gives the client a legally defensible record.
You cannot audit what you do not know exists. Asset discovery is the foundation of everything that follows.
nmap -sn 10.0.0.0/16 -oA discovery/host_sweep --reason
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This sends ICMP echo requests, TCP SYN to port 443, TCP ACK to port 80, and ICMP timestamp requests to identify live hosts without triggering deep packet inspection. For environments that filter ICMP aggressively, layer in TCP-based discovery:
nmap -PS22,80,443,8080,3389 -PA80,443 -PE -PP -PU53 10.0.0.0/16 -oA discovery/host_sweep_aggressive
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Once live hosts are identified, enumerate open ports and running services across the full port range:
nmap -sV -sC -p- --min-rate 1000 -T4 -iL discovery/live_hosts.txt -oA enumeration/full_service_scan
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The -sC flag runs Nmap's default script engine (NSE) against discovered services, which will extract banners, identify TLS versions, enumerate SMB shares, and pull SNMP community strings automatically.
For environments with detection controls, consider slower, more evasive scanning:
nmap -sS -T2 -f --data-length 32 -p 1-65535 --randomize-hosts -iL discovery/live_hosts.txt -oA enumeration/stealth_scan
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Active scanning leaves traces in firewall logs and SIEM alerts. Passive enumeration supplements active discovery by analyzing existing traffic without generating new packets.
Deploy Zeek (formerly Bro) on a span port or network tap to capture conn.log, dns.log, and ssl.log data, then extract unique internal IPs communicating across segments:
zeek -r capture.pcap local && cat conn.log | zeek-cut id.orig_h id.resp_h id.resp_p proto | sort -u
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This surfaces assets that do not respond to active probes but are actively communicating, which is particularly valuable for identifying unauthorized devices and shadow IT.
Technical scanning alone cannot tell you whether the network is designed securely. Architecture review examines how the network is segmented, how traffic flows between zones, and whether controls align with the principle of least privilege.
Firewall rule analysis: Export firewall configurations and audit rulesets for overly permissive rules, shadowed rules, and rules that allow traffic that should be denied. Tools like Tufin, Algosec, or even a custom Python script can parse Cisco ASA, Palo Alto, or Fortinet configs and flag rules that match patterns like any any permit.
VLAN segmentation: Verify that production, development, guest, and OT/ICS networks are in separate VLANs with inter-VLAN routing controlled at a managed layer 3 device with explicit ACLs.
Routing table analysis: Collect routing tables from core switches and routers. Look for unexpected routes, default routes pointing to untrusted segments, and redistribution between routing protocols without filtering.
show ip route
show ip bgp summary
show ip ospf neighbor
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DMZ architecture: Confirm that public-facing services sit in a properly configured DMZ with no direct routing between the DMZ and the internal trusted zone.
If your architecture shows flat networks where a compromised workstation can reach domain controllers, production databases, and management interfaces without restriction, that is a critical finding regardless of any other controls in place. The network security professionals at Redfox Cybersecurity routinely find flat or minimally segmented networks even in organizations with mature security programs.
With a complete asset inventory and an understanding of the network architecture, you can now run targeted vulnerability scans.
Unauthenticated scanning surfaces only what is visible from the network. Authenticated scanning logs into each target using provided credentials and inspects the system internally, which dramatically increases finding coverage.
Configure a Greenbone Vulnerability Management (GVM) scan with SSH credentials for Linux targets and WMI/DCOM credentials for Windows targets, then run:
gvm-cli --gmp-username admin --gmp-password <password> socket \
--xml "<create_task><name>Authenticated Scan</name>\
<config id='daba56c8-73ec-11df-a475-002264764cea'/>\
<target id='<target_id>'/></create_task>"
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Nuclei is a fast, template-driven scanner ideal for identifying specific vulnerability classes across large IP ranges. Run it against web-facing services discovered during enumeration:
nuclei -l enumeration/web_targets.txt \
-t cves/ \
-t exposures/ \
-t misconfiguration/ \
-severity critical,high,medium \
-rate-limit 100 \
-o reports/nuclei_findings.txt
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Nuclei's template library is actively maintained and covers thousands of CVEs, exposed admin panels, default credentials, and misconfigurations. It is particularly effective for web application components running on network infrastructure like router management interfaces, network cameras, and industrial control panels.
For Windows environments, use CrackMapExec to audit authentication posture across the domain without triggering lockouts:
crackmapexec smb 10.0.0.0/24 --gen-relay-list relay_targets.txt
crackmapexec smb 10.0.0.0/24 -u '' -p '' --shares
crackmapexec smb 10.0.0.0/24 -u guest -p '' --users
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Null session access to shares, guest authentication, and exposed user enumeration are all findings with direct remediation paths. Unauthenticated access to administrative shares like C$ and ADMIN$ is a critical severity finding in any audit.
Vulnerability scanners identify known CVEs. Manual firewall testing identifies rule logic failures that no scanner will find.
Many organizations invest heavily in inbound controls while leaving egress filtering nearly wide open. Test which ports and protocols can exit the network from a workstation-class machine:
for port in 21 22 23 25 53 80 443 445 1080 3389 4444 8080 8443 9001; do
nc -zv -w2 <external_listener_ip> $port 2>&1 | grep -E "open|refused|timed out"
done
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Any port that reaches your external listener represents a potential command-and-control channel for an attacker who has compromised an internal host. Legitimate business needs rarely require workstations to initiate outbound connections on port 445 or 4444.
If the environment uses 802.1Q trunking, test for VLAN hopping vulnerabilities using Yersinia:
yersinia -G
# Select 802.1Q attack, then "Sending 802.1Q double-encapsulated packet"
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Double-tagging attacks allow an attacker on a default VLAN to inject traffic into a different VLAN, effectively bypassing segmentation. The fix is to change the native VLAN to an unused VLAN ID on all trunk ports and explicitly disable DTP on access ports.
Stolen or weak credentials are involved in the vast majority of network breaches. The audit must examine authentication posture across the entire environment.
Pull domain password policy via LDAP:
ldapsearch -x -H ldap://10.0.0.5 -D "auditor@domain.local" -w 'Password1' \
-b "DC=domain,DC=local" "(objectClass=domainDNS)" \
pwdHistoryLength lockoutThreshold lockoutDuration minPwdLength
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A lockout threshold above ten attempts, a minimum password length below twelve characters, or no requirement for complexity are all reportable findings under most frameworks.
Test network devices for default credentials using Hydra against SSH and Telnet interfaces:
hydra -L wordlists/default_users.txt -P wordlists/default_passes.txt \
-M enumeration/network_devices.txt ssh -t 4 -w 3 -o reports/hydra_ssh.txt
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Common default credential pairs like admin:admin, cisco:cisco, and admin:password still exist in production networks with surprising frequency, particularly on infrastructure that was stood up quickly during rapid expansion or acquired through M&A activity.
If wireless networks are in scope, the assessment must cover both the security of the wireless infrastructure itself and the potential for rogue access points to provide unauthorized entry into the wired network.
airmon-ng start wlan0
airodump-ng wlan0mon --write wireless/capture --output-format pcap,csv
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Review captured beacons for:
For WPA2-Enterprise deployments, verify that the RADIUS certificate is properly validated on client devices. Without certificate pinning, clients are vulnerable to evil twin attacks using a rogue RADIUS server.
A network can have excellent controls in place and still fail catastrophically if no one is watching. The audit should evaluate whether logging is comprehensive, centralized, and actually monitored.
Check for centralized logging: Verify that firewall, switch, router, and endpoint logs are forwarded to a SIEM. Spot-check log timestamps against authoritative NTP sources to ensure forensic integrity.
Test detection coverage: Perform a low-noise action that should trigger an alert, such as a single Nmap SYN scan against a monitored host, then verify whether the SIEM generated an alert and whether anyone responded. The gap between what organizations think their detection coverage is and what it actually is tends to be one of the more uncomfortable findings in an audit, and it is one that the security operations teams at Redfox Cybersecurity address as a core component of every engagement.
Review retention policies: Security incidents often require log data from weeks or months prior to discovery. Verify that log retention meets both the organization's incident response requirements and any applicable compliance mandates.
Technical findings without business context are noise. The audit report translates raw findings into prioritized, actionable recommendations that stakeholders at every level can understand and act on.
Each finding should include:
Do not assign the same priority to every critical finding. A critical vulnerability on an internet-facing, unauthenticated service with a public exploit is categorically different from a critical vulnerability on an isolated internal system with no known public exploit. Layer in threat intelligence, asset criticality, and compensating controls to produce a prioritized remediation roadmap that is realistic given the organization's resources.
An audit that ends with a report and no follow-up validation is an incomplete engagement. Remediation validation confirms that the fixes that were applied actually address the root cause rather than just the symptom.
Schedule re-testing for all critical and high severity findings within thirty days of report delivery. For medium and low findings, a ninety-day re-test cycle is generally appropriate. Re-test using the same techniques and commands that produced the original finding to ensure direct comparability.
Track remediation status in a structured format, whether that is a spreadsheet, a ticketing system, or a purpose-built vulnerability management platform. Every finding should have an owner, a target remediation date, and a current status.
A network security audit is not a checkbox activity. When done properly, it combines deep technical work across discovery, enumeration, architecture review, vulnerability scanning, authentication testing, and detection assessment to produce a defensible, evidence-backed picture of your network's actual risk exposure.
The steps covered here, from scoping and passive discovery through wireless assessment and remediation validation, represent the lifecycle of a mature, professional audit. Each step builds on the last, and skipping any one of them leaves gaps that attackers are trained to find.
Organizations that conduct regular, comprehensive network security audits are measurably better positioned to detect intrusions early, contain their impact, and demonstrate due diligence to customers, partners, and regulators. If your organization is due for a network audit or has never had one conducted by an independent third party, the network security team at Redfox Cybersecurity can scope and deliver an engagement calibrated to your environment, compliance requirements, and risk tolerance.
Redfox Cyber Security Inc.
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Delaware 19901,
United States.
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