Senior Backend Engineer, Firewall

Horizon3 is a fast-growing, remote cybersecurity company dedicated to the mission of enabling organizations to proactively find, fix and verify exploitable attack vectors before criminals exploit them. Our flagship product, the NodeZeroTM platform, delivers production-safe autonomous pentests and other key assessment operations that scale across the largest internal, external, cloud, and hybrid cloud environments. NodeZero has been adopted by organizations of all sizes, from small educational institutions to government agencies and Global 100 enterprises. It is used by IT Ops/SecOps teams, consulting pentesters, and MSSPs and MSPs.

We are a fusion of former U.S. Special Operations cyber operators, startup engineers & operators, and formerly frustrated cybersecurity practitioners. We're committed to helping solve our common security problems: ineffective security tools and false positives, resulting in alert fatigue, blind spots, "checkbox” security culture, cybersecurity skills shortage, and the long lead time and expense of hiring outside consultants. Collectively, we are a team of learn-it-alls, committed to a culture of respect, collaboration, ownership, and results.

We're hiring a Senior Firewall Engineer to be the blue team voice inside the Firewall team. You'll sit between Product and Engineering as the person who defines what "correct" means. When an attack technique is detected, you decide what remediation that claim requires. Your judgment becomes the ground truth.

This is not a coding role and it is not a product management role. Product owns the roadmap, Engineering owns the implementation, and our AI researchers own how the agents reason. You own the domain truth all three depend on, and you make it concrete enough to build and measure against. If you've spent your career being the person in the room who knows how the tools really behave, this is a seat where that knowledge teaches a system instead of firefighting alerts.

• Partner with Product to turn firewall effectiveness and tuning ambitions into concrete, buildable requirements.

• Translate blue team workflows and pain into prioritized product outcomes, and push back when a proposed feature or agent behavior would not hold up in a real SOC.

• Define acceptance criteria for detection, effectiveness, and tuning features, and validate releases against them before customers see them.

• Serve as the standing domain reference for Engineering and AI research: available for design reviews, technique questions, and vendor behavior questions.

• Own deep, current knowledge of major firewall platforms (i.e. AWS WAF, Palo Alto PAN-OS, Fortinet FortiOS, Cisco Secure Firewall, and Check Point Quantum) at the management console, policy/configuration, traffic and logging, and API levels.

• Maintain fluency in how policy evaluation and enforcement work in each product, including rule order, zones, objects, NAT, security profiles, exceptions, and differences between default and hardened configurations.

• Define vendor-specific policy semantics so a recommended rule or configuration change has equivalent intent across platforms that model policies differently.

• Track platform releases, policy and API changes, new inspection and threat-prevention capabilities, and vendor guidance; keep our supported coverage model current as vendors ship.

• Define what a correct firewall tuning recommendation looks like, ex. blocking the validated attack path while preserving legitimate traffic, and evaluate remediation output against that standard.

• Partner with the Attack team so attack-path validation, firewall coverage, and remediation guidance stay grounded in current adversary tradecraft and real network behavior.

• 6+ years in firewall engineering, network security, security operations, incident response, or threat hunting, with meaningful time spent as a practitioner rather than an advisor.

• Hands-on experience administering and tuning enterprise firewall platforms in production (i.e. Palo Alto PAN-OS, Fortinet FortiGate/FortiOS, Cisco Secure Firewall, or Check Point Quantum) including rulebases, NAT, segmentation, and policy exceptions.

• Deep understanding of how network and SOC teams use firewall policy outcomes and traffic/threat logs for triage, containment, and investigation.

• Fluency in false-positive and false-negative tradeoffs, overly permissive rules, service-availability risks, and how to assess firewall policy effectiveness and coverage.

• Strong working knowledge of MITRE ATT&CK and network-control coverage frameworks, with a clear view of where they help and where they can mislead.

• Solid understanding of post-compromise attacker behavior and how it appears in network traffic and firewall telemetry, and how firewall controls can limit command-and-control, lateral movement, and data exfiltration.

• Demonstrated experience shaping a product or platform as a domain expert, whether in a security vendor, an internal tooling team, or a detection engineering function.

• Ability to influence without authority. You will not manage the engineers or own the roadmap, and you will still be expected to move both.

• Exceptional technical writing. Most of your leverage here comes from written artifacts — requirements, methodology docs, labeling guides, tuning content.

• Comfort translating between audiences: engineers, AI researchers, product managers, SOC analysts, and executives.

• Enough scripting ability, ideally Python, to query APIs, inspect telemetry, and prototype an analysis.

• Comfort with SQL and with reasoning over large volumes of event and telemetry data.

Please note this job description is not designed to cover or contain a comprehensive listing of activities, duties or responsibilities that are required of the employee. Duties, responsibilities, and activities may change at any time with or without notice.

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