FortiGate Misconfiguration: 3 Hours of Production Firewall Vulnerability

In the IT world, human error is an ever-present variable. A single distraction, a sudden context switch, and critical infrastructure can find itself exposed to unimaginable risks. This is exactly what happened when a FortiGate misconfiguration left a production firewall vulnerable for a staggering 3 hours. A 30-minute maintenance window, a temporary any-any policy intended to last just 5 minutes, and a support ticket arriving at the least opportune moment: these were the ingredients of a nightmare scenario that put an entire network at risk. Timely detection and mitigation of such incidents are crucial for enterprise security, especially in environments with thousands of endpoints, where every minute of exposure amplifies potential damage. This incident underscored the importance of rigorous change management processes and proactive, not just reactive, monitoring to protect critical infrastructure from errors that can have significant consequences. According to a 2024 SANS Institute report, 68% of cybersecurity incidents in 2024 were caused by configuration errors.

Prerequisites / Test Environment

The incident occurred in a complex production environment managed by an organization with approximately 2,000 workstations and over 300 VMware VMs. The firewall involved was a FortiGate 600F, configured for high availability, responsible for filtering traffic between the internal network and the internet. The FortiOS version was 7.2.5. Monitoring tools included a SIEM (Wazuh) and a centralized log management system. While the incident is real, specific details have been generalized for confidentiality, but the methodology and lessons learned are applicable to any enterprise environment using FortiGate firewalls.

The Context: Planned 30-Minute Policy Update

It was a Thursday afternoon, a low-activity period to minimize user impact. The goal was to implement a new firewall policy to allow traffic to a new cloud service, which required some connectivity tests. The maintenance window was set for only 30 minutes, with a well-defined rollback plan in case of issues. To facilitate initial tests and verify basic connectivity, a temporary any-any policy was created with a scheduled deactivation timer for 5 minutes, just enough time to confirm that traffic wasn’t blocked elsewhere in the chain. This practice, while risky, is sometimes adopted in complex environments to quickly isolate connectivity problems.

The Error: An any-any Policy Active for 3 Hours

The problem arose when, halfway through the maintenance window, an urgent call came in from a user reporting a complete blockage of access to a critical application. The team’s attention immediately shifted to that issue, which required in-depth analysis and separate troubleshooting. In this hectic phase, the manual deactivation of the temporary any-any policy was forgotten. The 5-minute timer, for some reason (likely an unsaved CLI interface or an unexpected reboot), did not activate, or perhaps it hadn’t been persistently set. The policy, which should have been deleted or disabled after a few minutes, remained active, opening a critical vulnerability in the security perimeter.

To check for active any-any policies on the firewall, you can use the following command:

get firewall policy | grep -A5 'srcaddr: all' | grep 'dstaddr: all'

This command lists policies with srcaddr and dstaddr set to all, indicating potential exposure. It’s a fundamental check to perform regularly, or before every maintenance window.

How We Discovered It (with Security Logs, Not an Alert)

The misconfiguration was not discovered through a proactive alert from the firewall or the SIEM, as it should have been. No system had flagged the prolonged activation of such a permissive policy. The revelation came from a retroactive review of security logs, conducted hours after the incident, following internal reports of unusual traffic. The security team, analyzing the logs, noticed a surge in inbound and outbound traffic not justified by normal activities. This traffic included port scan attempts from external IPs, SSH and RDP connections to internal servers that should not have been exposed, and even outbound traffic to suspicious destinations from internal hosts, suggesting potential pre-existing compromises that had exploited the exposure window. According to the IBM Cost of a Data Breach Report 2023, 45% of security breaches are not detected within the first 24 hours, and the average detection time is 206 days.

To analyze anomalous traffic logs, commands like these can be used:

execute log filter field dstport 22
execute log filter field action accept
execute log display

These commands allow filtering logs for specific destinations (e.g., port 22 for SSH) and actions (accept), helping to identify unexpected traffic.

What Passed Through the Firewall in Those 3 Hours

During the 3 hours of exposure, logs recorded a series of suspicious activities. In addition to automated port scans by botnets, brute-force attempts were detected on services like SSH and RDP, which were temporarily exposed on some internal machines. In particular, a spike in outbound connections was observed from some internal servers that should have only communicated with internal resources or specific cloud services. This traffic, likely part of a botnet or pre-existing dormant malware, exploited the any-any policy to communicate with command and control (C2) servers. Although no critical data exfiltration was found, the incident highlighted the severity of a misconfiguration and how quickly attackers (even automated ones) can exploit new vulnerability windows.

Remediation and Damage Analysis: What Was Reachable

The first remediation action was immediate: the any-any policy was identified and disabled with absolute priority. Subsequently, a detailed forensic analysis was initiated to determine the extent of the damage. This included reviewing system logs of exposed internal servers, analyzing network traffic captured during the exposure period, and scanning for vulnerabilities on all potentially compromised hosts. Fortunately, thanks to internal network segmentation and the presence of other security controls (like EDR on endpoints), the impact was contained. However, it was confirmed that some servers had been targeted by access attempts and that a couple of machines had managed to establish suspicious outbound connections. These hosts were isolated, inspected, and remediated.

The Process We Changed to Prevent Recurrence

The incident triggered a complete review of firewall change management processes. The most important lesson was the absolute necessity of a foolproof process that doesn’t rely solely on an operator’s memory or goodwill. We implemented a multi-level approval system for every firewall change, including peer review and formal approval. Additionally, an automatic alert system was introduced to immediately flag the activation of any-any or overly permissive policies, with a forced deactivation timer if they are not removed within a predefined period (e.g., 15 minutes). Every change now requires a configuration backup before application and a tested rollback plan.

For configuration backup and rollback, the commands are:

execute backup config ftp <ip> <path> <user> <pass>
execute restore config ftp <ip> <path> <user> <pass>

These commands are vital for having a quick restore point in case of errors.

Firewall Change Management: The 5 Rules I Now Use

After the incident, I standardized a set of rules for firewall change management that I apply in every enterprise context:

Peer Review: Every firewall configuration change must be reviewed and approved by at least one other experienced engineer. This reduces the probability of errors and ensures a critical second look.
Rollback and Test Window: Every change must have a well-defined and tested rollback plan. Before applying a change in production, it must be tested in a staging environment that replicates production as closely as possible. The maintenance window must include sufficient time for a complete rollback.
Automatic Alerts for Permissive Policies: Implement a monitoring system that generates immediate alerts if any-any or excessively broad IP/port range policies are activated. These alerts must include rapid escalation and, if possible, an automatic deactivation mechanism after a predefined time if no manual confirmation is provided.
Detailed Documentation: Every change must be exhaustively documented, including the rationale, expected impact, tests performed, and the rollback plan. This documentation is crucial for future audits and shared team knowledge.
Post-Deploy Audit: After every significant change, perform a configuration audit to verify that policies have been applied correctly and that there are no unintended side effects. This includes analyzing logs to detect anomalous traffic.

These rules, based on direct experience and standards like ISO 27001:2022, aim to create a robust process that minimizes the risk of human errors and critical misconfigurations, which, according to the Verizon DBIR 2024 report, represent one of the primary causes of data breaches.

Common Errors and Troubleshooting

Common errors in FortiGate configurations often include forgetting to save changes (config system global and end or save), incorrect policy order (traffic is processed by the first matching policy), and excessive use of any or all objects that create security holes. Another frequent error is not testing changes in a staging environment, leading to production outages. For troubleshooting, it’s essential to start by analyzing logs (diag debug flow and get log traffic), checking interface status (get system interface), and always having a recent configuration backup for quick recovery.

Conclusions with Operational Takeaways

The FortiGate misconfiguration incident is a powerful reminder: cybersecurity is not just about advanced technologies, but also about processes and attention to detail. A seemingly small error can have enormous consequences. The operational takeaways are clear: invest in robust change management, implement proactive monitoring systems to detect misconfigurations in real-time, and continuously train personnel on operational security. Do not rely solely on technology; the human factor remains the most critical vulnerability. An infrastructure’s resilience depends on the ability to learn from mistakes and transform them into concrete procedural improvements. Every minute of exposure counts, and a well-oiled process can make the difference between a contained incident and a large-scale disaster.

Updated: July 2026

External link: FortiGate Documentation