Key Firewall Best Practices

5 min. read

Key firewall best practices include:

  1. Harden and configure firewalls properly.
  2. Adopt a customized, phased deployment strategy.
  3. Enhance and regularly update firewall protocols.
  4. Regularly review and update access controls.
  5. Implement a comprehensive logging and alert mechanism.
  6. Establish backup and restoration protocols.
  7. Align policies with compliance standards.
  8. Subject firewalls to regular testing.
  9. Conduct routine firewall audits.

Harden and Configure Firewalls Properly

Firewall best practice: ensure hardening before deployment by reviewing the OS, following rule setup guidelines, and configuration checks.

The process of hardening and securing firewalls begins long before deployment into a network. This involves analyzing the operating system that underpins the firewall, ensuring it’s free from vulnerabilities. Following trusted guidelines from recognized authorities like standard-setting organizations and vendors who produce your firewall software or hardware can ensure that firewall rules are set up accurately and thoroughly. Don't forget web servers, which are often prime targets for cyberattacks and require meticulous firewall configurations to safeguard them from potential threats. A system that isn’t robust from the outset can be the weakest link in an otherwise secure network security architecture.

Firewall configuration, on the other hand, is a dynamic and ongoing task. A firewall’s effectiveness is determined not just by its inherent features but also by how it’s set up. Poor configuration can inadvertently create loopholes for cyber adversaries, letting potentially malicious network traffic through. Security teams should conduct regular firewall configuration checks, making the necessary adjustments based on the evolving threat landscape.

Adopt a Customized, Phased Deployment Strategy

Deploying a firewall isn’t a one-size-fits-all proposition. The deployment strategy should be based on an organization’s unique infrastructure and requirements. Ensuring that firewall interfaces correctly with both Layer 2 and Layer 3 networks is vital for creating an adaptable security posture. Zones derived from these connections can help simplify and customize firewall policy applications.

Transitioning to enhanced firewall configurations must be methodical. An abrupt shift can lead to unexpected disruptions, potentially disrupting internet access for users and degrade user experience. A phased deployment strategy can mitigate these risks.

Enhance and Regularly Update Firewall Protocols

Firewall best practice: Update protocols and engage with cybersecurity community to stay informed.

Outdated protocols like telnet or unsecured SNMP configurations can be potential gateways for breaches. Continually evaluating and updating protocols is imperative.

Beyond technical configurations, maintaining a vigilant eye on the threat landscape is crucial. Human intervention plays a pivotal role here. Firewall administrative teams should not simply reply on automated systems, but actively engage with the cybersecurity community. Staying informed about emerging threats, vulnerabilities specific to firewall models, and vendor-recommended patches can protect the network from potential security challenges.

Ensure Rigorous Traffic Control

Firewalls are pivotal in regulating who and what interacts with a network. The general principle for robust security is to deny all traffic by default, only permitting known and trusted entities. By classifying traffic—whether from external sources, internal departments, or specific business units—an organized, systematic flow is established.

Monitoring doesn't end with classification. Constant vigilance is required to detect anomalies in access patterns or traffic flow. Any deviation from the norm could indicate potential threats or breaches, making real-time monitoring and swift response capabilities invaluable.

Regularly Review and Update Access Controls

Firewall best practice: review and adapt access controls to ensure only necessary personnel have access.

As organizations evolve, so does the nature and number of individuals requiring access to critical systems like firewalls. Regular access control list reviews ensure that only the necessary personnel have access, minimizing potential internal vulnerabilities. Limiting access also means that in case of breaches, the number of potential internal sources is controlled, aiding swift resolution.

However, access controls aren’t just about restriction. They’re also about ensuring users access resources they need, ensuring smooth operations. As roles evolve, access needs might change. Adapting controls responsively ensures that operations aren’t hampered while security remains uncompromised.

Implement a Comprehensive Logging and Alert Mechanism

Comprehensive logging mechanisms provide a detailed trail of all outbound and inbound traffic, offering invaluable insights into patterns, including anomalies in source IP addresses and destination IP addresses, potential vulnerabilities, and even internal threats. This documentation can also inform future policy decisions.

Logs are meaningful only if acted upon. Real-time alerts for anomalies ensure swift action. Regularly scheduled log reviews can identify potential threats before they manifest into security breaches. Real-time alerts coupled with periodic reviews ensure a robust, responsive firewall security mechanism.

Establish Backup and Restoration Protocols

Firewall best practice: implement and regularly test restoration protocols to ensure backups are functional.

Backups form the crux of a resilient security posture. They ensure that configurations, policies, and other critical data can be swiftly restored, preserving the security and integrity of the internal network.

It’s imperative to set in place detailed restoration protocols. These procedures should be documented, accessible, and regularly tested. By conducting test restorations, the organization can ascertain the integrity of backups, ensuring they aren’t just placeholders but functional tools in crisis scenarios.

Align Policies with Compliance Standards

Compliance is a double-edged sword. While it sets the minimum security standards an organization must adhere to, relying solely on compliance metrics can be myopic. Regularly aligning firewall configurations and policies with prevailing regulations ensures the organization is both meeting the requisite standards and prepared for audits.

Compliance isn’t static. As cyber threats evolve, so do regulations. Integrating auxiliary security mechanisms, staying updated on regulatory changes, and routinely adjusting firewall settings ensures an organization remains both compliant and secure.

Subject Firewalls to Regular Testing

Firewall best practice: regularly subject firewalls to testing to ensure they function as intended. This includes pen testing.

Regularly subjecting firewalls to rigorous testing scenarios like path analysis ensures they function as intended. Such proactive measures help in identifying potential weak spots, offering insights into areas of improvement.

Periodic penetration testing is another invaluable tool. By simulating real-world cyber-attack scenarios, organizations can gauge the robustness of their firewall defenses, ensuring they are well-prepared for genuine threats.

Conduct Routine Firewall Audits

Audits serve as both a check and balance. Regular checks guarantee that the software, firmware, and log functionalities remain up-to-date and in optimal working condition. This boosts firewall effectiveness and prepares the organization for external inspections.

A structured approach to policy modifications, informed by these audits, ensures changes enhance security rather than compromise it. Every adjustment should be methodical, with its implications thoroughly considered, ensuring that security remains uncompromised.


Firewall rules can be categorized into several types, but a basic classification might include:
  • Allow or Permit Rule
  • Deny or Block Rule
  • Implicit Deny Rule
  • Logging Rule
In the real world, firewalls often have many more than just four rules. They can have complex rule sets tailored to organizational needs, security postures, and network architectures.
A firewall strategy is a comprehensive approach to designing, implementing, and managing firewall configurations and rules to ensure the security and functionality of an organization's network.
  • Network Layout: Understand where a firewall fits best.
  • Rule Design: Regularly review and update rules.
  • Default Settings: Change default credentials.
  • Updates: Regularly patch.
  • Logging: Monitor logs for unusual activities.
  • Access Control: Limit who can manage the firewall.
  • Management Security: Use secure methods.
  • Backups: Maintain regular backups.
  • Physical Access: Restrict physical access.
Yes, hackers can sometimes get past firewalls. Skilled hackers can exploit vulnerabilities or misconfigurations to bypass firewall protections. However, organizations can take many proactive measures, such as adopting advanced ML-based NGFW solutions, regular updates, audits, and penetration testing, to enhance their effectiveness and reduce the risk of breaches.
The first rule in a firewall, often considered the most fundamental rule, is the "default deny" or "implicit deny" rule. This rule blocks all traffic by default and only allows traffic that is explicitly permitted by subsequent rules. By starting with a default deny stance, you ensure that only traffic you've specifically allowed can pass through the firewall.