Senior Attack Engineer, Internal Systems

Get to Know Us

Horizon3.ai 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.

An Overview

We're seeking a Senior Attack Engineer who blends deep software engineering expertise with a passion for cybersecurity. In this role, you’ll independently lead complex internal network and Active Directory attack projects in NodeZero, our autonomous pentesting platform.

Internal enterprise networks and Active Directory remain key targets in modern breaches, and it is exactly where our customers most need NodeZero to find and safely prove exploitable attack paths. The environments we operate in are hardening fast, while tradecraft continues to evolve across network protocols, identity systems, management planes, and hybrid environments. We need someone who can research and weaponize real-world vulnerabilities and misconfigurations into reliable product capabilities.

You'll design and build production-grade systems that drive the offensive capabilities of the NodeZero platform. You'll own complex attack capabilities from research and technical design through production delivery and ongoing operation, making consequential technical decisions within the internal network scope. You'll also strengthen the team through proactive mentorship, thoughtful code reviews, and improvements to our engineering and research practices.

This is not consulting or manual pentesting. The goal is to turn cutting-edge, often manual techniques into safe, reliable, repeatable autonomous attacks that scale across the largest internal environments in the world. If you love both breaking internal network infrastructure and building scalable software to automate it, this is the seat.

What You’ll Do

• Research and develop novel attack capabilities for integration into the NodeZero platform, focusing on autonomous red teaming, internal network breach techniques, and offensive security automation.

• Research emerging internal tradecraft (network protocol exploitation, Active Directory abuse, management-plane attacks, delegation, credential access, and hybrid identity pivots) and turn it into production attack content.

• Design, build, and maintain production-grade Python systems, making clear tradeoffs between attack effectiveness, operational safety, reliability, scalability, and maintainability.

• Acquire, configure, and exploit modern, hardened internal test environments to validate and demonstrate complex attack scenarios.

• Monitor public vulnerability databases and threat intelligence sources to stay current on emerging threats and incorporate them into internal network attack modules.

• Extend and maintain platform architecture and graph data models for new identity, privilege-escalation, and lateral-movement paths.

• Help shape the team's coverage priorities using customer needs, threat intelligence, and emerging techniques; scope deliverable projects and proactively raise risks and tradeoffs.

• Mentor teammates and improve team processes, code quality, architectural standards, and research safety practices.

• Partner cross-functionally with engineers, product managers, and customer-facing teams to resolve issues, enhance features, author technical documentation, and drive customer value.

What You’ll Bring

• Deep, hands-on offensive security experience against internal enterprise networks and Active Directory, from initial foothold through domain and enterprise compromise.

• Expert-level proficiency in Python for large-scale development and a track record of shipping and maintaining tested, documented, production-quality code.

• Strong command of internal network attack techniques, including network protocol exploitation, privilege escalation, lateral movement, and credential access.

• Experience with object-oriented design, API integration, data structures, and building scalable system components in fast-paced product environments.

• Experience designing complex software components or systems, accounting for extensibility, operational safety, performance, and long-term maintenance, and explaining the reasoning behind architectural decisions.

• A track record of independently leading complex, high-impact technical projects with significant risk, making sound decisions under ambiguity, and identifying business implications and delivery risks before they become critical issues.

• Strong written and verbal communication, including clear technical documentation and the ability to explain design choices, risks, and tradeoffs to engineers and non-technical stakeholders.

• Demonstrated investment in teammates' growth through proactive mentorship, architectural feedback, and code reviews, along with experience improving team processes, tooling, or technical standards.

• Offensive security and software engineering background with a strong passion for turning security research into safe, maintainable