Senior WAF Engineer, Autonomous Defense

Horizon3.ai; United States; Remote; USD 140,000 - 210,000; Full time

Job summary

Horizon3.ai is seeking a Senior Web Application Firewall Engineer to join our remote cybersecurity team. You will be the blue team voice between Product and Engineering, defining what “correct” means when an attack technique is detected and deciding remediation requirements.

This role focuses on WAF policy tuning, domain expertise across major platforms, and collaboration with AI researchers to ground the system in real-world adversary behavior.

Qualifications

• 5+ years in application security, security engineering, security operations, incident response, or threat hunting.

Responsibilities

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

Skills

AppSec experience

WAF tuning

Incident response

Threat hunting

SOC analysis

Python scripting

Tools

AWS WAF

Cloudflare WAF

F5 Advanced WAF

Imperva

Akamai App & API Protector

FortiWeb

ModSecurity + OWASP CRS

Job description

Get to Know Us

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 & MSPs.

Get to Know Us

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 & 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.

What You’ll Do

We're hiring a Senior Web Application 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.

Responsibilities

PRODUCT DIRECTION & REQUIREMENTS

• Partner with Product to turn WAF 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.

FIREWALL & NETWORK POLICY DOMAIN EXPERTISE

• Own deep, current knowledge of major WAF platforms (i.e. AWS WAF, Cloudflare WAF, F5 Advanced WAF, Imperva, Akamai App & API Protector, FortiWeb, and ModSecurity with OWASP CRS) at the management console, rule/policy configuration, request logging, and API levels.
• Maintain fluency in how rule evaluation and enforcement work in each product, including rule priority and ordering, managed rule groups, custom rules, rate-based rules, exclusions and exceptions, count/monitor vs. block modes, request body inspection limits, and differences between default and hardened configurations.
• Define vendor-specific rule semantics so a recommended rule or configuration change has equivalent intent across platforms that model policies differently (e.g., web ACLs and rule groups vs. security policies and signature sets vs. rule chains).
• Track platform releases, rule and API changes, new managed rule sets, bot and API protection capabilities, and vendor guidance; keep our supported coverage model current as vendors ship.
• Define what a correct WAF tuning recommendation looks like, e.g. blocking the validated exploit (including realistic encoding and payload variants) while preserving legitimate application traffic, and evaluate remediation output against that standard.
• Partner with the Attack team so exploit validation, WAF coverage, and remediation guidance stay grounded in current adversary tradecraft and real application behavior.

What You’ll Bring

FIREWALL & NETWORK SECURITY EXPERTISE

• 5+ years in application security, security engineering, security operations, incident response, or threat hunting, including 2+ years of hands‑on experience administering and tuning WAF platforms in production.
• Hands‑on experience administering and tuning WAF platforms in production (i.e. AWS WAF, Cloudflare WAF, F5 Advanced WAF, Imperva, Akamai App & API Protector, FortiWeb, or ModSecurity with OWASP CRS), including custom rules, managed rule groups, rate‑based rules, exclusions, and count‑to‑block rollout.
• Deep understanding of how AppSec and SOC teams use WAF rule outcomes and request logs for triage, containment, and investigation.
• Fluency in false‑positive and false‑negative tradeoffs, overly permissive rules and exclusions, application‑availability risks, and how to assess WAF policy effectiveness and coverage.
• Strong working knowledge of the OWASP Top 10, MITRE ATT&CK (e.g., T1190), and application‑control coverage frameworks, with a clear view of where they help and where they can mislead.
• Solid understanding of web attack behavior and how it appears in HTTP requests and WAF telemetry, and how WAF controls can limit exploitation of public‑facing applications, injection attacks, credential stuffing and bot abuse, and API abuse.

PRODUCT & COLLABORATION

• 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.

TECHNICAL FLUENCY

• Enough scripting ability, ideally Python, to query APIs,