12 Best Practices for a Corporate Firewall Review

Identify Audit Plan Objectives and Scope

Every firewall audit begins by identifying the purpose and objectives. For example, you may engage in audits for the following reasons:

• Compliance with security standards and industry frameworks, like PCI DSS, HIPAA, NIST, GDPR, SOX, or NERC CIP

• Reduce the attack surface by decommissioning unused, shadowed, or outdated firewall rules

• Optimize performance and functionality by simplifying firewall rulebases and deleting unnecessary rules

Understand Network Topology

A key information security control is creating demilitarized zones (DMZ), or security zones, that reduce the likelihood that cyberattacks will impact multiple subnets.

However, these DMZs make establishing a baseline for firewall reviews more challenging. Understanding the network topology involves reviewing firewall:

• Locations
• Connectivity
• Roles
• Vendors and models 

Gather Audit Documentation

To streamline firewall reviews, the following information should be available for IT security stakeholders:

• Security policies: Internal controls detailing firewall best practices
• Firewall logs: Technical documentation showing protocols, IP addresses, subnets, and inbound/outbound traffic
• Risk assessments: Risk identification, review, and remediation activities
• Firewall rulesets and configurations: Including object groups, access control lists, and NAT rules
• Audit reports: Documents identifying previous audit findings or compliance reviews

Evaluate Firewall Rule Placement and Order

Firewall rules should be arranged logically, from highest priority at the top to lowest at the bottom. Best practices for firewall rule order typically include:

• Allow specific traffic first, using precise details like source IP addresses, destination IPs, ports, and TCP/UDP protocols
• Deny by default, using an explicit deny-all rule at the bottom of the firewall policy

Assess Firewall Rule Unused Objects

Unused objects include networks, subnets, services, applications, user groups, or connections not specified in the ruleset. These create vulnerabilities and increase the attack surface.

Analyze Access Control Lists (ACLs)

ACLs determine which traffic can enter the internal network. Overly permissive ACLs can introduce security risks. Best practices include:

• Limit source and destination traffic to only what is required
• Explicitly define IP address ranges or groups instead of using “any”
• Avoid rules that allow all traffic inbound or outbound
• Reduce open ports exposed to the internet

Review Roles and Access Privileges

To maintain least privilege, review user access control policies regularly. For privileged accounts and administrators, validate:

• Permissions remain consistent across firewall vendors
• Access was terminated for departed users
• Only authorized stakeholders can access the firewall console
• Role-based access and user authentication policies align with security posture goals

Review Change Management Procedures

Structured change management reduces misconfigurations. Each firewall policy change should include:

• Risks associated with the change
• Impact on network access and compliance requirements
• Remediation and mitigation strategies
• Reasons for the rule change
• Documentation of the who, why, and when for modifications

Harden Firewall Hardware and Operating Systems

Vulnerabilities in firewall firmware or the operating system can allow unauthorized access. Best practices include:

• Regular vulnerability scans
• Prioritized remediation for high-risk issues
• Applying patches and firmware updates in real time

Review Firewall Logs

Firewall logs provide insights into network traffic and security posture. To prevent information overload, configure logs to capture:

• Permitted, blocked, and dropped connections
• IDS/IPS alerts
• User authentication activity
• Unusual network traffic patterns

Logs should support both troubleshooting and compliance reporting for regulations like NIST, GDPR, and PCI DSS.

Review Risk Assessment Documentation

Before implementing new firewall rules, document a risk assessment. Best practices include:

• Analyzing business continuity risks
• Reviewing vulnerabilities in access controls
• Running “what-if” path analysis to validate rule placement
• Ensuring consistency with your change management process

Remediate Issues and Test New Firewall Rules

Remediation includes tightening overly permissive rules, removing shadowed rules, and applying corrective actions to firewall settings. Testing new rules in a staging environment ensures proper functionality without disrupting production systems.

Automated Documentation with Tufin

Tufin provides automation for firewall management and continuous compliance. With vendor-agnostic Unified Security Policies (USPs), automated risk assessments, and audit-ready reports, organizations can streamline security audits, reduce manual work, and maintain compliance with frameworks like NIST, PCI DSS, and HIPAA.

Tufin’s automation capabilities also help ensure consistent firewall configurations, optimize firewall rulesets, and mitigate security risks across hybrid and multi-cloud environments.

FAQs

What is a firewall audit and why is it important?

A firewall audit is a systematic review of firewall configurations, rules, and security policies to ensure they align with compliance requirements, cybersecurity best practices, and organizational business needs. Regular audits identify vulnerabilities, reduce the attack surface, and help maintain regulatory compliance.

How often should companies conduct a firewall review?

Organizations should conduct firewall reviews at least annually, though many industries—such as finance, healthcare, and utilities—require more frequent reviews based on PCI DSS, HIPAA, or NIST guidelines. Regular audits reduce misconfigurations, validate compliance, and improve real-time visibility into firewall settings.

What are best practices for firewall rules in an audit?

Best practices include using least privilege access, documenting firewall configurations, validating firewall logs, removing unused objects, limiting inbound/outbound traffic, and applying automation for continuous compliance monitoring.

How does NIST relate to firewall audits?

NIST frameworks reference firewalls as a foundational control for network security and risk management. Following NIST guidelines helps ensure firewall configurations align with an organization’s information security policy, access controls, and vulnerability management processes.

What role does automation play in firewall audits?

Automation streamlines firewall management by reducing human error, accelerating risk assessments, and generating audit reports for stakeholders and regulators. Tools like Tufin provide workflows, compliance checklists, and real-time validation of firewall changes.

Wrapping Up

Firewall reviews are a critical part of maintaining strong network security, reducing vulnerabilities, and complying with frameworks like NIST, PCI DSS, and HIPAA. By combining a clear firewall audit checklist with automation tools, organizations can optimize security posture, streamline compliance, and mitigate risks more effectively.