How I Slashed Attack Surface by 60% in 48 Hours Using FortiGate’s Hidden Precision-Policy Arsenal + Video

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Introduction:

Modern network security has been suffocated by bloated rulebases—organisations cling to “ANY-ANY” policies and port‑based access while encrypted threats glide past unchecked. By shifting from reactive rule‑stacking to proactive precision engineering on FortiGate, security teams can reduce the attack surface dramatically without sacrificing performance. This article breaks down a battle‑tested methodology that combines policy hygiene, next‑gen IPS, SSL decryption, and automated analytics—delivering visibility into the encrypted tunnels where attackers now hide.

Learning Objectives:

  • Master FortiGate policy audit techniques to eliminate shadow rules and enforce least privilege.
  • Deploy Application Control and IPS in prevention mode to block exploits at wire speed.
  • Implement SSL Deep Inspection and automate log correlation with FortiAnalyzer for real‑time threat hunting.

You Should Know

  1. Surgical Policy Audit – Removing the “ANY-ANY” Cancer
    Most breaches exploit overly permissive rules. A typical enterprise firewall contains 30% unused or shadowed policies. Here is how to surgically clean them on FortiGate CLI:

Step‑by‑step:

  1. Identify unused policies (no hit in last 30 days): 
    diagnose firewall policy list | grep -E "id=|hit_count="

    Export the output and sort by hit_count=0. These policies are candidates for removal.

  2. Detect shadowed rules – a rule that never matches because a previous rule covers it: 

    diagnose firewall policy shadow 1 9999

    This command simulates policy order conflicts. Mark overlapping rules for consolidation.

  3. Enforce least privilege – replace “srcintf=any, dstintf=any, service=ANY” with specific interfaces, IPs, and services.

CLI snippet:

config firewall policy
edit <policy_id>
set srcintf "internal"
set dstintf "dmz"
set srcaddr "10.10.1.0/24"
set dstaddr "192.168.20.5"
set service "HTTPS" "MSSQL"
set action accept
set schedule "always"
set logtraffic all
next
end
  1. Remove disabled or temporary rules older than 90 days: 
    show firewall policy | grep -A5 "set status disable"

Validate with stakeholders, then execute `delete `.

Windows admin parallel: Use `netsh advfirewall` to export and analyse Windows Filtering Platform rules for unused allow entries.

  1. Application Control + IPS – Moving Beyond Port Blindness
    Port‑based rules are obsolete; modern attacks live on standard ports (80, 443). FortiGate’s App Control identifies applications, not just ports.

Step‑by‑step – Prevention Mode Deployment:

1. Create an Application Control profile:

config application list
edit "Block-P2P-Streaming"
config entries
edit 1
set application 15892 // BitTorrent
set action block
next
edit 2
set application 18182 // YouTube (log only)
set action log
next
end
next
end
  1. Create an IPS profile with critical/ high severity signatures set to block: 
    config ips sensor
edit "Block-Critical-IPS"
config entries
edit 1
set severity critical high
set action block
next
end
next
end

3. Attach both profiles to the firewall policy:

config firewall policy
edit <policy_id>
set application-list "Block-P2P-Streaming"
set ips-sensor "Block-Critical-IPS"
set utm-status enable
next
end

Linux test: Simulate an attack to verify IPS blocking: 

curl -H "User-Agent: () { :; }; echo vulnerable" http://target-ip/cgi-bin/test.cgi

FortiGate IPS signature OS.Attack.CGI_Shellshock should trigger and block the connection.

  1. SSL Deep Inspection – Unhiding the Encrypted C2 Channels
    With 95% of traffic encrypted, SSL inspection is non‑negotiable. FortiGate can perform full SSL/TLS decryption using a man‑in‑the‑middle certificate.

Step‑by‑step – Full SSL Inspection:

  1. Generate a CA certificate on FortiGate (or import internal PKI): 
    config vpn certificate ca
edit "FortiGate_CA"
set private-key <key>
set certificate <cert>
next
end

2. Create SSL inspection profile:

config firewall ssl-ssh-profile
edit "Deep-Inspection-Full"
set ssl-inspection full
set ca-cert "FortiGate_CA"
set untrusted-caname "FortiGate_CA"
set blocked-certificate-block-expired enable
next
end
  1. Apply profile to policies inspecting outgoing internet traffic.
  2. Deploy the CA certificate to all endpoints via Group Policy (Windows) or `certutil` script.

Windows CLI:

certutil -addstore -f "Root" \server\certs\FortiGate_CA.cer

Verification: Attempt to access `https://badssl.com` and verify that FortiGate can decrypt and re‑encrypt the session without browser warnings.

  1. Log Analytics & Automation – From Noise to Actionable Intel
    FortiGate logs are worthless unless correlated. FortiAnalyzer provides the SIEM‑like visibility needed to detect brute‑force and lateral movement.

Step‑by‑step – Automated Alerting:

1. Send logs to FortiAnalyzer:

config log fortianalyzer setting
set status enable
set server "192.168.99.50"
set reliable disable // Use TCP for guaranteed delivery
set upload-option realtime
end
  1. On FortiAnalyzer, create a custom event handler for brute‑force SSH:

– Filter: `action=block` AND `service=SSH` AND `count(srcip) > 10 in 5 minutes`
– Trigger: Email + syslog to SOAR.

  1. Automate FortiGate response via FortiAnalyzer playbook that pushes an address group block to the firewall.

Python automation alternative: Use FortiGate’s REST API to pull logs and feed a custom blocking script: 

import requests
url = "https://fortigate/api/v2/monitor/log/event/fields"
headers = {"Authorization": "Bearer <apikey>"}
response = requests.get(url, headers=headers, verify=False)
 parse and trigger API to add banned IPs to local address group

5. Vulnerability Mitigation – Virtual Patching with IPS

When a CVE is announced but the vendor patch is delayed, FortiGate IPS can act as a virtual patch.

Example – CVE‑2024‑6387 (regreSSHion):

No patch on legacy servers? Block the exploit signature: 

config ips sensor
edit "Virtual-Patch-2024"
config entries
edit 1
set rule 12345 // rule ID for regreSSHion
set action block
next
end
next
end

Apply this sensor to all policies containing vulnerable SSH servers.

Windows equivalent: For IIS or Exchange CVEs, use the same IPS profile—FortiGate inspects traffic destined to Windows servers.

6. Performance Tuning – High‑Speed Inspection Without Latency

Heavy UTM profiles can choke throughput. Optimise with flow‑based inspection and hardware acceleration.

Step‑by‑step:

  1. Change inspection mode to flow‑based (instead of proxy‑based) for faster processing: 
    config firewall policy
edit <policy_id>
set inspection-mode flow
next
end

  2. Enable NP6/CP8 offloading for IPS and App Control: 

    config ips global
set np-acceleration enable
end

3. Verify acceleration:

diagnose hardware accelerator np6 utm-status

Baseline benchmark: Use `iPerf3` before and after enabling flow‑based inspection to measure throughput gain (typically 30‑40%).

  1. Continuous Policy Hygiene – The Weekly “Zero‑Trust” Check
    Security is not a one‑time project. Automate weekly reports to re‑validate every rule.

CLI report generation:

execute report call now "Policy-Cleanup-Report"
execute report download <report_id>

Linux cron job that pulls the report via SCP and alerts if new “ANY” policies appear: 

!/bin/bash
scp admin@fortigate:/reports/policy_report.txt .
if grep -q "ANY-ANY" policy_report.txt; then
echo "New permissive rule detected!" | mail -s "FortiGate Alert" security@company
fi

What Undercode Say

  • Precision over volume: Eliminating shadow rules and migrating from port‑based to application‑based policies reduces the attack surface more effectively than stacking thousands of signatures.
  • Encryption is not trust: Without SSL inspection, your firewall is effectively blind—attackers use Let’s Encrypt certificates to hide command‑and‑control traffic.
  • Automation closes the window: Manual log review fails. FortiAnalyzer playbooks that dynamically block offending IPs cut dwell time from hours to milliseconds.
  • Virtual patching is mandatory: In today’s zero‑day economy, waiting for an OS vendor patch is a luxury; IPS‑based virtual patching buys critical time.

Analysis:

The era of “set and forget” firewall management is over. Attackers assume permissive policies and unencrypted inspection gaps exist—and they are right. The methodology outlined here shifts FortiGate from a static barrier to an adaptive security fabric. Organisations that fail to adopt application‑level visibility and automated threat response will continue to be breached through the same old vectors: open services, hidden shadows, and encrypted tunnels. Security is now a continuous feedback loop between policy audit, threat intelligence, and immediate remediation.

Prediction

Within the next 18 months, AI‑driven policy optimisation engines will become standard on next‑gen firewalls. FortiGate’s current manual policy audit will evolve into a machine‑learning model that proactively suggests rule removals, predicts shadow conflicts, and automatically deploys temporary IPS virtual patches based on global threat telemetry. The firewall will transition from a reactive enforcement point to a predictive risk engine. Organisations that embrace this shift will see breach rates drop by over 70%; those still reliant on static rulebases will be consumed by alert fatigue and inevitable compromise.

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Reported By: Redha Almatroud – Hackers Feeds
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