Fortigate Firewall Audit

FortiGate Firewall Security Policy Audit

Policy-audit-driven analysis of FortiGate/FortiOS firewall policies. Unlike generic firewall checklists that check for open ports and default-deny, this skill evaluates the FortiOS-specific security architecture: Virtual Domain (VDOM) segmentation, UTM profile binding on every allow policy, FortiGuard signature freshness, and SD-WAN SLA-based traffic steering security implications.

Covers FortiOS 7.x+ on FortiGate hardware appliances and FortiGate-VM virtual instances. For FortiManager-managed deployments, the audit addresses ADOM hierarchy and policy package consistency. Reference references/policy-model.md for the full VDOM/UTM inspection chain and references/cli-reference.md for read-only CLI commands.

When to Use

• Post-change policy review after rule additions or VDOM topology changes
• VDOM segmentation audit verifying inter-VDOM link isolation and per-VDOM policy independence
• UTM profile coverage assessment — finding allow policies without antivirus, IPS, or web-filter inspection
• SD-WAN security evaluation — confirming SLA violations do not steer traffic around security controls
• FortiGuard license and connectivity validation — ensuring signature databases are current
• HA cluster security posture check — verifying firmware parity, config sync, and session-sync settings
• Quarterly or annual compliance audit requiring per-policy justification
• Pre-upgrade baseline before FortiOS major version changes

Prerequisites

• Read-only administrative access to FortiOS CLI (or diagnose-level privilege for runtime state)
• Understanding of the VDOM topology — which VDOMs exist, their function (management, traffic, DMZ), and expected inter-VDOM links
• Knowledge of expected UTM profile assignments per policy category (internet-bound, inter-zone, intrazone)
• For FortiManager-managed environments: access to the ADOM with visibility into policy packages
• Awareness of SD-WAN configuration — SLA targets, member interfaces, and health-check definitions
• Running configuration committed — audit evaluates the active configuration, not pending changes

Procedure

Follow this audit flow sequentially. Each step builds on prior findings. The procedure moves from VDOM architecture inventory through per-VDOM rule-level analysis to UTM coverage, FortiGuard health, SD-WAN security, and HA posture.

Step 1: VDOM Architecture Inventory

Collect all VDOMs and their roles.

config vdom
edit root
end
get system status

On a multi-VDOM system, list all VDOMs:

diagnose sys vd list

For each VDOM, record: name, type (traffic/management/admin), assigned interfaces (physical and virtual), inter-VDOM link pairs, and VDOM resource limits (session count, CPU quota). Identify the management VDOM — this is where FortiGuard updates, logging, and administrative access are configured.

Check inter-VDOM links:

show system vdom-link

Inter-VDOM links function as virtual interfaces connecting two VDOMs. Traffic crossing a VDOM link is subject to the receiving VDOM's firewall policies — verify that inter-VDOM traffic is not bypassing inspection.

Verify VDOM resource limits to detect unbounded VDOMs that could starve other VDOMs during volumetric events:

config global
get system vdom-property

Flag any VDOM without explicit resource limits in a multi-VDOM deployment.

Step 2: Firewall Policy Rule-by-Rule Analysis

For each VDOM, retrieve the full policy table:

config vdom
edit <vdom-name>
show firewall policy

FortiOS evaluates firewall policies top-down by sequence number within each VDOM. The first matching policy is applied. Evaluate each policy against these criteria:

• Overly permissive policies: Policies with srcaddr "all", dstaddr "all", service "ALL", and action accept are Critical findings — they accept all traffic on all ports with no restriction.
• Missing UTM profiles: Allow policies without antivirus, web-filter, application-control, or IPS profile binding pass traffic uninspected. Check utm-status, av-profile, webfilter-profile, application-list, and ips-sensor on each allow policy.
• Disabled policies: Policies with status disable still occupy sequence numbers and create audit confusion. Flag for cleanup.
• Schedule-based policies: Policies with schedule other than always may create time-window security gaps. Verify schedules align with intended access windows.
• Implicit deny: FortiOS has an implicit deny (policy ID 0) at the bottom of each VDOM's policy table. Verify it is logging traffic for visibility into denied connections.

Check for unused policies using hit count data:

diagnose firewall iprope show 100004 <policy-id>

Policies with zero hits over 90+ days are cleanup candidates.

Step 3: UTM Profile Binding Audit

For each allow policy in every VDOM, verify that UTM inspection profiles are bound. The goal is zero allow policies without threat inspection.

Check each allow policy for these profile bindings:

• Antivirus (av-profile): File-based malware scanning. Required on all internet-bound and inter-zone policies.
• Web Filter (webfilter-profile): URL categorization and blocking. Required on all policies permitting HTTP/HTTPS.
• Application Control (application-list): Application identification and enforcement. FortiOS equivalent of App-ID.
• IPS (ips-sensor): Intrusion prevention signatures. Required on all allow policies carrying untrusted traffic.
• Email Filter (emailfilter-profile): Anti-spam for SMTP/IMAP/POP3. Required on email-carrying policies.
• DLP Sensor (dlp-sensor): Data loss prevention pattern matching. Required where sensitive data egress risk exists.
• SSL Inspection (ssl-ssh-profile): Determines whether encrypted traffic is decrypted for UTM inspection. Without SSL inspection set to deep-inspection, AV and IPS see only connection metadata on HTTPS.

Summarize coverage: count allow policies with full UTM binding versus allow policies with partial or no UTM profiles. Calculate the UTM coverage ratio.

Check the inspection mode per VDOM:

config vdom
edit <vdom-name>
get system settings | grep inspection-mode

Flow-based mode applies all UTM in a single pass (faster, less thorough). Proxy-based mode buffers and inspects fully (more thorough, more resource intensive). The mode affects which UTM features are available and their efficacy.

Step 4: FortiGuard Service Validation

FortiGuard provides the signature databases that UTM profiles depend on. Stale signatures reduce detection efficacy.

get system fortiguard-service status
diagnose autoupdate versions

Verify the following signature databases are current:

Check FortiGuard connectivity:

diagnose debug rating
execute ping service.fortiguard.net

If FortiGuard is unreachable, all cloud-dependent features (web filter rating queries, FortiSandbox cloud, outbreak prevention) operate in degraded mode using cached data only.

Verify the update schedule:

show system autoupdate schedule

Best practice is scheduled updates every 1–4 hours for AV and daily for IPS/App-Control. Manual-only updates are a finding.

Step 5: SD-WAN SLA and Rule Security

If SD-WAN is configured, evaluate security implications of traffic steering.

config vdom
edit <vdom-name>
show system sdwan

Review SD-WAN components:

• SLA targets and health checks: Examine each health check definition (protocol, server, threshold). Verify health-check servers are reachable and meaningful for the SLA metric (latency, jitter, packet loss).

diagnose sys sdwan health-check

• SD-WAN rules: Each rule maps traffic to preferred WAN members based on SLA status. Review rule priorities and the tie-break method.

diagnose sys sdwan service

• Fail-open behavior: When all SLA members fail, SD-WAN rules may fall through to standard routing. Determine whether this fallback path still traverses security inspection. A fail-open that routes around a security VDOM or UTM-inspecting policy is a Critical finding.

• SD-WAN + firewall policy interaction: SD-WAN selects the egress interface, but firewall policies still control access. Verify that firewall policies cover all SD-WAN member interfaces. A policy that references a specific interface may not match when SD-WAN steers traffic to an alternate member.