8 Best Practices for Firewalls to Keep the Network Safe

A firewall best practices guide may explain your company's security policy goals to security stakeholders, maintain compliance with industry requirements, and enhance your company's cybersecurity posture.

We'll go over some information and 8 security practices to show you how to secure your firewall.

1. Secure the Firewall by Hardening It and Properly Configuring It

The provider hardens the operating systems of most all-in-one firewall security solutions. If you're using a software firewall, make sure you patch and harden the operating system first.

After hardening an operating system, security administrators must verify that the firewall has the correct configurations.

2. Make a Firewall Deployment Plan

For implementing zero-trust security concepts, firewalls are an essential tool. In a macro-segmented network, they monitor and regulate data traffic across network boundaries. In layer 3 routed firewall deployments, the firewall acts as a gateway linking many networks, while in layer 2 bridge firewall deployments, it integrates and filters devices within a single network.

A perimeter firewall will include an internet-connected external zone, other internal interfaces connected to internal networks, and, possibly, a DMZ network connection. The firewall's network interface connects to these networks when you deploy it. You can then simplify the firewall policy by using these zones. You can then tweak the firewall policy to add more granular control as desired.

It will be essential to manage the firewall. "Will the firewall require a special management interface as well?" is an important matter to consider. Only dedicated, secure networks should have access to lights-out management and serial console access.

Finally, a solitary firewall can cause a single point of failure (SPOF). When you deploy two or more in a High Availability (HA) cluster, you maintain security even if one fails. A hyperscale network security solution is a better alternative since it continuously leverages the resources of each cluster member. Take this into account for networks with seasonal traffic surges.

3. Ensure the Firewall is Secure

Firewall and network protection are critical to maintaining a robust security infrastructure free from vulnerabilities. Follow these actions to protect your firewall:

  • Use a secure SNMP setup instead of insecure protocols like telnet and SNMP.

  • Regular backups of the database and configuration are necessary.

  • Audit changes to the system and sends logs to an external, secure, central SIEM server or firewall management solution through a secure Syslog for forensic analysis and reporting.

  • To avoid firewall detection during network scans, add a stealth rule to the firewall configuration.

  • Only allow specific hosts to have administrative access.

  • Vulnerabilities exist even in firewalls. Find out if the vendor is aware of any security vulnerabilities and any patches to address them.

4. Protect User Profiles

Cyber attackers frequently use account takeover as a tactic. Follow these steps to safeguard user accounts on your firewall:

  • Change default user-profiles and passwords.

  • Set up multi-factor authentication (MFA) and/or a strong password policy requiring complex passwords.

  • For firewall administrators, use role-based access control (RBAC). Grant and restrict access based on the user's requirements (i.e., auditors should only have read-only access, and DevSecOps teams should have their own access roles and accounts.)

5. Limit Zone Access to Authorized Traffic

A firewall's principal function is to enforce and regulate network segmentation authorization.

Firewalls can monitor and manage traffic flowing north/south across a network boundary. Zones in this micro-segmentation use case include external, internal, DMZ, and guest Wi-Fi. They could also be business units that connect via distinct internal networks, such as the data center, human resources, finance, or a production floor in a production facility equipped with Industrial Control Systems (ICS).

Firewalls in virtual clouds can inspect individual servers or apps that alter dynamically when instances are spun up. Web applications or databases can define zones in this micro-segmentation use case. A tag can set the virtual server's function to work in a firewall policy without human intervention, minimizing the possibility of manual configuration errors.

Firewalls restrict access in macro and micro installations by establishing a firewall policy rule that defines access depending on traffic source and destination. The firewall can define the service or port that the application will use. The default ports for web traffic, for example, are 80 and 443. Only these ports should be accessible; all other ports should be out of limits. Safelisting the authorized traffic is an option.

Since it's practically difficult to define which ports are necessary for Internet access, outbound traffic from an enterprise to the Internet is more challenging for a safelisting security policy. Blocklisting is a more common solution for an egress security policy, prohibiting known bad traffic and allowing everything else by a firewall policy rule that says "accept all."

Besides IP and port limitations, activate other security capabilities on the next-generation firewall (NGFW) to detect known malicious sites. URL filtering and application control are two examples. For example, this can permit access to Facebook but not to its games.

6. Ensure that The Firewall Policy and Its Implementation Conform to Industry Standards

Firewalls are subject to particular regulations. Virtual private networks (VPNs) to encrypt data in transit, antivirus to block malicious programs, and intrusion detection and prevention systems (IDS/IPS) to identify any network intrusion attempts are just a few examples. Security firewall best practices must meet these requirements, which may require extra security controls for any firewall in use.

PCI DSS, for example, mandates firewall zone-based rules for trusted and untrusted zones. This mandate includes using a perimeter firewall, like a DMZ, to separate any wireless networks from the cardholder data environment. The following are some additional PCI DSS requirements:

  • Detect and prohibit fake source IP addresses from entering the network using anti-spoofing tools. Block incoming traffic from a source address on one of the internal networks on the external interface, for example.

  • Using Network Address Translation (NAT) and eliminating route ads for private networks, do not reveal private IP addresses and routing information to unauthorized users.

  • Clean out any unneeded, outdated, or incorrect rules every six months, and ensure that all rule sets only allow permitted services and ports.

  • Ensure that cardholder data is secure across public networks.

  • Apply any security patches from the vendor. Install essential security fixes no later than one month after the release. (Companies may wish to adjust this to update when a patch is available, given how quickly cyber attackers exploit known vulnerabilities.) An NGFW that changes IPS signatures automatically can defend entire networks from new vulnerabilities.)

  • There must be procedures in place to control access based on the need to know and job responsibilities.

  • Maintain a log of all network resources and cardholder data accesses.

  • Sync all essential system clocks and times using time-synchronization technology.

  • Test security systems and processes regularly.

7. Conduct a Test to Verify the Policy and Identify any Vulnerabilities

It isn't easy to imagine how a more comprehensive security strategy would handle a new connection. Path analysis tools exist and may help search and find rules in the security management system.

Some security management systems issue a warning when a duplicate item appears or declines to install a rule that hides another. Test your policy regularly to ensure it is finding unused and duplicate items.

Moving top hit rules further up in the inspection sequence can optimize firewall policies in top-down order. Review the policy regularly to improve the performance of your firewall.

Finally, undertake frequent penetration testing to detect any network security threats and any extra measures that may be necessary to secure your organization with the firewall.

8. Examine the Software or Hardware and the Logs

Regular audits are necessary to ensure that software and firmware are up-to-date and the logs have proper operational configurations. The following are some best practices for these assessments:

  • Create a systematic change control process for altering the security policy to ensure security is not at risk.

  • Rules having a set in the source, destination, or port could be a security vulnerability. Update these to include the rule's specific source, destination, or service.

  • Organize the security policy into sections or levels to make it easy to review.

  • Clean-up rules that match the layer's intent should be present at the end of the section or level (i.e., allow-all or deny-all).

  • Include comments and names to help identify the original intent of each rule.

  • Enable logging to improve network traffic tracking and to provide additional visibility for forensics.

  • Examine audit logs and reports regularly to see changes to the firewall policy.

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