Zero Trust Security Is Monroe-Minky: Common Firewall Misconfigurations

Zero Trust security is based on the principle of strictly controlling access, continuous monitoring, and ensuring a well-configured firewall to ensure that gaps in security are minimized.

Firewall Misconfigurations Put Businesses at Risk

When properly configured, firewalls can be an effective security measure against attackers, but they can also create vulnerabilities when not configured properly. And without even realizing it, many organizations compromise their Zero Trust security postures to lower their overall network performance.

When you’re renting firewalls, servers, or routers, you want to make sure they’re configured the right way. Following are the major firewall misconfigurations to be aware of that will sabotage Zero Trust security — and how to avoid them.

1. Overly Permissive Rules

Setting overly permissive rules is the most common firewall misconfiguration. Many businesses have overly permissive network traffic through their firewall, which violates the principle of least privilege:

• Permitting all traffic by default – This defeats the entire purpose of a firewall. All traffic should be denied by default and only allowed according to specific business needs.
• Any in rule – Allowing ANY in the source or destination or in ports makes it easy to move threats across the network unnoticed.
• Old or unused rules left over – Unnecessary firewall rules create loopholes that cybercriminals can perpetrate.
• Wide open access for roamers – While roaming access is necessary, it’s also risky, and open VPN or RDP access could compromise an entire network.

How to Fix It

• Deny everything by default and only allow what is absolutely necessary.
• Audit and clean up your rules to remove obsolete ones.
• Use specific IPs, ports, and services rather than generic access rules.
• Implement granular access controls for least privilege access.

2. No Network Segmentation

A core component of a strong Zero-Trust security model is isolated network zones where, if an attacker gets past one segment, they cannot roam freely throughout your entire network. However, misconfigured firewalls commonly result in:

• Flat networks – If all devices and servers exist in the same network zone, a hacker will be able to move laterally without restrictions.
• Rented firewalls and servers not segmented – Businesses renting firewalls or servers must have segmentation rights and enforce policies accordingly.

How to Fix It

• Segregate sensitive zones with VLANs and subnets.
• Enforce strict communications barriers between segments.
• Apply firewall rules by segment, segregating flow by department or data.
• Implement micro-segmentation to minimize the attack surface with access restrictions between workloads and applications.

3. Lack of Monitoring

Well-configured firewalls can become a liability when not monitored. Most organizations put a firewall in place and take it at face value, without reviewing it regularly. This leads to:

• Undetected anomalies — If no one monitors firewall logs, breaches go undetected.
• Undetected misconfigurations – Firewalls change over time, and without monitoring, risky misconfigurations can go unchecked.
• Slower response to attacks – Without real-time alerts, businesses may only notice a breach when it’s too late.

How to Fix It

• Turn on firewall logging and event tracking to monitor suspicious activity.
• Enable automated alerts and threat intelligence to catch real-time threats.
• Conduct regular log analysis to identify anomalous behavior.
• Deploy SIEM tools (Security Information and Event Management) for deeper security insights.

4. Ignoring Outbound Traffic

The vast majority of businesses are only concerned with protecting inbound traffic because they think threats only come from external attackers. However, ignoring outbound firewall rules can lead to significant security breaches:

• Failing to restrict outbound connections — Malware can easily move stolen data out of the network if no outbound rules are in place.
• Botnet communications – Infected computers could communicate with a hacker’s command and control (C2) server.
• Employees surfing the web – With no outbound filtering, employees can visit sites that reintroduce malware into the enterprise.

How to Fix It

• Restrict all access to the Internet – outbound access should only be allowed if necessary.
• Block malicious sites with DNS filtering and web proxies.
• Monitor for abnormal outbound traffic patterns, such as attempts to exfiltrate large amounts of data.
• Apply appropriate controls at the application layer to ensure only allowed applications communicate with the internet.

5. Failure to Update Policies

Threats change, and so should firewall rules and policies. Many businesses fail to:

• Regularly review and update policies — Outdated firewall policies might not include rules that cover new cybersecurity threats.
• Configure settings for new devices or services – If you rent firewalls, servers, or routers, a new configuration may be necessary for each implementation.
• Delete expired security rules – Rules that are no longer needed can open security holes.

How to Fix It

• Make periodic policy reviews to eliminate outdated rules.
• Test firewall rules before applying them to a production environment.
• Employ automated policy enforcement to ensure security configurations are up to date.

Final Thoughts

Avoiding these firewall misconfigurations is crucial for ensuring Zero Trust security and minimizing security gaps. Businesses must be diligent in configuring their firewalls properly, segmenting their network, consistently monitoring activity (especially if open-air access is available), and staying informed about policy changes when renting firewalls, servers, and routers.

Following best practices for firewalls is essential in preventing security breaches, protecting sensitive data, and building a robust Zero Trust security model from the ground up.