Firewall Configuration Security: Protecting Your Network's Blueprint
Learn why firewall configuration files are high-value targets for attackers, what sensitive data they contain, and how to protect this critical infrastructure information from theft and exploitation.
When attackers compromise a network firewallFirewall🌐Security system that monitors and controls network traffic based on predetermined rules., stealing the configuration file is often one of their first objectives. These files are far more valuable than they might appear—they contain a complete blueprint of your network security architecture, revealing everything from internal network topology to firewall rules, VPN configurations, and even hashed administrator passwords. The recent Fortinet CVE-2025-59718 and CVE-2025-59719 exploitation campaign demonstrates exactly why: after bypassing authentication, attackers immediately downloaded configuration files from compromised devices.
In this guide, you will learn what information firewall configurations contain, why attackers prize this data, and practical steps to protect your organization's configuration files from theft and exploitation. Whether you manage Fortinet, Cisco, Palo Alto, or other firewall platforms, these principles apply across vendor boundaries.
What Firewall Configuration Files Contain
A firewall configuration file is essentially a complete snapshot of your security device's setup. Understanding what's in these files helps explain why protecting them is so critical.
Network Architecture Information
Configuration files reveal your network's internal structure, including IP addressing schemes and subnet configurations, VLAN assignments and segmentation strategies, routing tables showing how traffic flows between network segments, NAT (Network Address Translation) rules mapping internal to external addresses, and interface configurations identifying which ports connect to which networks. This information gives attackers a map of your environment, helping them understand where valuable assets reside and how to move between network segments.
Security Policy Rules
The heart of any firewall is its rule set—the policies that determine what traffic is allowed or blocked. Configuration files expose access control lists defining permitted and denied traffic, application control policies identifying allowed applications, content filtering rules and URL category restrictions, intrusion prevention system (IPS) signatures and exceptions, and any "permit any" rules or overly permissive policies that create security gaps.
Attackers analyze these rules to identify allowed pathways through the firewall—traffic that won't be blocked or inspected. They look for rules that allow broad access, disabled security features, or exceptions that might be exploitable.
VPN Configurations
Remote access and site-to-site VPN configurations are particularly valuable to attackers. Configuration files may reveal IPsec tunnel configurations including encryptionEncryption🛡️The process of converting data into a coded format that can only be read with the correct decryption key. algorithms and pre-shared keys, SSL VPN portal configurations and access policies, split tunnelingSplit Tunneling🔐A VPN feature allowing some traffic through the VPN while other traffic uses your regular connection. settings that determine what traffic goes through the VPN, client IP pool assignments for remote users, and authentication backend configurations (LDAP, RADIUS servers).
With this information, attackers may be able to configure their own VPN clients to connect to your network, or identify weaknesses in your VPN security that could be exploited.
Administrative Credentials
While modern firewalls don't store passwords in plaintext, configuration files typically contain hashed administrator passwords, API keys and tokens for integrations, SNMP community strings, and certificates and their associated private keys (in some configurations). If administrators use weak passwords, the hashes can potentially be cracked using dictionary attacks or rainbow tables, providing persistent access to the device.
Service and Integration Details
Configuration files also reveal how your firewall integrates with other systems: authentication server addresses (Active Directory, LDAP, RADIUS), logging and SIEM server destinations, threat intelligence feed configurations, FortiCloudFortiCloud📖Fortinet's cloud-based management and services platform that provides centralized management, logging, reporting, and single sign-on capabilities for Fortinet security products. or other cloud management connections, and high availability and cluster configurations. Each integration point represents another potential attack vector that adversaries can explore.
Why Attackers Target Configuration Files
The exfiltration of firewall configurations during the Fortinet exploitation campaign reveals sophisticated attack planning. These files serve multiple purposes for threat actors.
Reconnaissance for Future Attacks
Configuration files provide attackers with a detailed map for planning targeted intrusions. Rather than stumbling blindly through a network, they can study the configuration offline to identify high-value targets based on network segmentation, find the path of least resistance through security controls, understand which monitoring might detect their activities, and plan lateral movementLateral Movement🛡️Techniques attackers use to move through a network after initial compromise, seeking additional systems to control and data to steal. between network segments.
Security Control Bypass
Knowing exactly what security rules exist allows attackers to craft their activities to avoid detection. They can identify which ports and protocols are allowed through the firewall, find exceptions in IPS or content inspection rules, understand what traffic is logged versus what passes silently, and discover any "shadow IT" or legacy rules that might provide unexpected access.
Persistent Access
Extracted credentials—even hashed—can provide long-term access if they can be cracked. Attackers may also use the configuration to identify alternative authentication paths, VPN access methods, or management interfaces that could provide access even after the initial vulnerabilityVulnerability🛡️A weakness in software, hardware, or processes that can be exploited by attackers to gain unauthorized access or cause harm. is patched.
Intelligence for Sale
Configuration files have value on underground markets. Initial access brokers may sell this intelligence to ransomware operators or other threat actors, who can then use the detailed network maps to execute more effective attacks. This is why configuration theft—even without immediate exploitation—should be treated as a serious security incident.
Protecting Firewall Configuration Files
Given the sensitive nature of configuration files, organizations should implement multiple layers of protection to prevent unauthorized access and detect potential theft.
Restrict Management Interface Access
The most effective protection is ensuring attackers cannot reach management interfaces in the first place. Never expose firewall management interfaces to the public internet—the Fortinet attackers could only exploitExploit🛡️Code or technique that takes advantage of a vulnerability to cause unintended behavior, such as gaining unauthorized access. the vulnerabilities because management access was reachable. Best practices include binding management interfaces only to internal management networks, using out-of-band management networks segregated from production traffic, implementing jump hosts or bastion servers for administrative access, and using VPN with multi-factor authentication for remote management.
Implement Strong Authentication
Defense in depthDefense in Depth🛡️A security strategy using multiple layers of protection so that if one layer fails, other layers continue to provide security. means even if management interfaces are accessible, strong authentication provides additional protection. Use multi-factor authentication for all administrative access, implement role-based access control to limit who can view or export configurations, create individual administrator accounts (no shared credentials), and use long, random passwords that resist offline cracking if hashes are extracted.
Encrypt Configuration Backups
Configuration files should be encrypted both in transit and at rest. When exporting configurations for backup, use the firewall's built-in encryption options. Most platforms support password-protecting exported configurations. Store backups in secure locations with appropriate access controls, and use encrypted channels (SFTP, SCP) when transferring configurations to backup systems.
Monitor Configuration Access
Implement comprehensive logging and alerting for configuration-related activities. Log all successful and failed login attempts to management interfaces, configuration view or export operations, configuration changes, and administrative session activities. Forward these logs to a SIEM and create alerts for suspicious patterns such as configuration exports outside of change windows or from unexpected source IPs.
Implement Configuration Version Control
Using configuration management tools that track changes provides both security and operational benefits. Solutions like FortiManager, Cisco DNA Center, or vendor-agnostic tools like Ansible with version control maintain complete history of configuration changes, enable quick identification of unauthorized modifications, support rapid rollback if malicious changes are detected, and provide audit trails for compliance.
If Your Configuration Has Been Stolen
If you suspect configuration files have been exfiltrated—whether through the Fortinet vulnerabilities or any other compromise—take these steps immediately.
Rotate All Credentials
Change all administrator passwords immediately using new, strong passwords. Regenerate any API keys or tokens. Update SNMP community strings. If pre-shared keys for VPN tunnels were in the configuration, coordinate with partners to rotate them. Assume that any credential in the configuration has been compromised.
Assess What Was Exposed
Review the configuration to understand what information attackers now have. Identify any particularly sensitive information such as VPN pre-shared keys, connections to critical systems, or weak security policies. Prioritize remediation based on what presents the highest risk.
Review and Harden Security Policies
Since attackers now know your security rules, consider whether any policies should be strengthened. Remove overly permissive rules that were identified during configuration review. Add additional security layers to compensate for exposed architecture. Consider network segmentation changes if internal structure was revealed.
Increase Monitoring
Enhance monitoring for the specific attack paths revealed in the configuration. Watch for traffic patterns that match allowed firewall rules, attempted connections from IP ranges associated with the initial attack, and VPN connection attempts using potentially compromised configurations.
Configuration Security Checklist
Use this checklist to evaluate and improve your firewall configuration security posture:
Key Takeaways
Firewall configuration files are high-value intelligence that attackers use for reconnaissance, security bypass, and persistent access. Protecting these files requires a layered approach:
