Firewall Compliance

Best Practices For Firewall Compliance

Since there’s a right way and a wrong way to set a firewall up, the following best practices are almost universal across most standards of firewall design.

#1: Deny All by Default

A “deny all” firewall policy is considered a best practice because it enforces the principle of least privilege, ensuring that only explicitly allowed traffic can pass through.

This minimizes the attack surface, reducing the risk of:

• Unauthorized access
• Malware infections
• Data breaches

By blocking all traffic by default and from there whitelisting what explicit communications are allowed, you maintain stricter control over network security from the get-go.

#2: Establish an Underlying Security Policy

Before redesigning firewall rules, organizations should establish a clear security policy.

This involves identifying sensitive data, determining how it should be protected, and defining operational requirements for various departments. A well-structured security policy should include:

• A data classification framework
• Access controls based on user roles
• A list of essential applications and services that require network access;
• A list of who is responsible for maintaining different parts of the security toolkit

By setting these guidelines upfront, organizations can reliably align firewall rules with their regulatory obligations.

#3: Implement Stateful Inspection

Stateful inspection tracks active connections and makes filtering decisions based on the context of the traffic.

Unlike static packet filtering, which examines packets in isolation of their surrounding requests, stateful inspection analyzes traffic patterns, verifying that packets are part of a legitimate session. This approach is powered by a dynamic state table of active connections.

Stateful firewalls provide more intelligent filtering thanks to this table.

#4: Don’t Rely on Default Settings

Databases and data flows look different depending on each organization; since a firewall needs to sit between sensitive networks and the public Internet, the internal firewall policies need to be changed accordingly.

When purchasing a firewall off-the-shelf, many organizations install it alongside the default configurations.

However, these are often generic, widely known, and may contain unnecessary open ports or permissive rules – all of which attackers can exploit. Customizing settings allows organizations to align firewall rules with specific business needs, and minimize the attack surface.

These adjustments should follow the underlying security strategy already put in place. Firewall rules can be customized along four different axes:

1. Source – Specifies the origin of the traffic (IP address or range).
2. Destination – Identifies the target IP address or range.
3. Service/Protocol – Defines the type of traffic and protocol (e.g., HTTP over TCP).
4. Connection Behavior – Covers both the connection state (new, established, etc.) and the action (allow or block) taken when the rule conditions are met.

#5: Don’t Just Install One Perimeter Firewall

Firewalls were traditionally installed around an organization’s central network.

Now, however, the underlying topology has changed so dramatically that this approach no longer works. Leaving endpoints without protection opens the door for account takeover and privilege escalation that then allows an attacker through the firewall.

Regulations like PCI DSS demand that personal firewall software be installed on all internet-connected computing devices. This should include custom configurations, alongside preventing the end-user from making any changes to the firewall software.

The firewall logs that result from this can then be fed into your wider security architecture, supporting compliance.

#6: Conduct Regular Firewall Audits

Regular firewall audits allow your organization to stay abreast of the changing security and network landscapes.

Conducting reviews on a regular, set schedule is one of the best ways to ensure a long-lasting firewall is as compliant as when the security team initially put the rules in place. To take it one step further, periodic penetration testing can simulate your real-world defenses against cyberattacks.

This allows you to uncover vulnerabilities that need immediate remediation.