Principal Attack Engineer, AI/LLM

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 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 are hiring a Principal Attack Engineer specializing in AI/LLM security to define the long-term technical direction for AI/LLM offense at Horizon3 . You will lead the company’s most complex and consequential efforts to break AI and agentic systems and turn that research into scalable, autonomous attack capabilities inside NodeZero, our autonomous pentesting platform. This is not consulting or manual pentesting; the goal is to establish durable, production-grade capabilities that materially expand how NodeZero finds and validates exploitable attack paths across customer environments. The focus is LLM-based applications: the chatbots, copilots, RAG pipelines, and AI agents that enterprises expose to employees, customers, and the internet.

You will operate at the intersection of company strategy and technical direction. You will shape the vision for AI/LLM offensive capabilities, partner with senior leadership on major technical and product decisions, and create the architecture, standards, and organizational alignment required for multiple teams to execute against that vision. This is a rare, company-wide role for a technical authority whose judgment influences the business and, where appropriate, the broader AI security field.

What You’ll Do

Company-wide Technical Leadership & Scope

• Define the long-term technical vision for AI/LLM offense and its role in NodeZero and the company’s broader product strategy.

• Partner with senior engineering, product, and business leadership to shape priorities, investment decisions, risk posture, and the roadmap for AI/LLM offensive capabilities.

• Set direction for the most complex, high-risk, and business-critical AI/LLM programs; establish the outcomes and decision principles against which teams execute.

• Lead cross-company initiatives that require alignment across Attack Engineering, Platform, Product, customer-facing teams, and other technical functions.

• Diagnose systemic blockers in architecture, process, operating model, or technical capability and drive durable resolution.

• Define company-wide standards for reliability, safety, observability, evaluation, testing, cost management, and operational readiness in LLM-powered offensive systems.

• Develop P5 engineers and other senior technical leaders, multiplying the organization’s capacity to reason about and deliver AI/LLM security capabilities.

• Communicate clearly with executives, technical leaders, and external stakeholders; bring the organization through major technical transitions with clarity and composure.

Attacking AI/LLM Systems

• Own NodeZero's coverage strategy for the OWASP Top 10 for LLM Applications (prompt injection, sensitive information disclosure, system prompt leakage, improper output handling, excessive agency, vector and embedding weaknesses, and data and model poisoning), and define where NodeZero should go beyond the list, particularly for multi-agent and tool-connected systems.

• Set the company’s research and productization agenda for breaking AI and agentic systems, balancing technical opportunity, customer impact, safety, and strategic differentiation.

• Identify novel, high-leverage attack classes and establish the frameworks, abstractions, and coverage models needed to make them repeatable in NodeZero.

• Direct the company’s approach to prompt injection, defense evasion, tool-use exploitation, context poisoning, remote code execution, data exfiltration, privilege escalation, and other agentic attack paths.

• Set technical direction for assessing AI infrastructure, including model serving, training pipelines, vector databases, GPU/MLOps tooling, and enterprise deployment architectures.

• Evaluate the strategic significance of model and supply-chain attacks such as poisoning, training-data extraction, adversarial inputs, and deployment-pipeline abuse, and determine how the company should respond.

• Establish a durable threat-modeling approach for agentic systems that accounts for trust boundaries, identities, permissions, tools, data sources, downstream systems, and business impact.

• Ensure research becomes safe, reliable, scalable product capability rather than remaining isolated expertise or one-off demonstrations.

• Serve as the definitive internal technical authority on the hardest and most novel AI/LLM offensive problems; where appropriate, represent the company through technical writing, talks, research, or open-source contributions.

Building with LLMs

• Set the long-term architecture for LLM-powered offensive applications, agentic workflows, evaluation systems, and their integration with NodeZero.

• Establish company-wide principles for cost, safety, hallucination guardrails, reliability, observability, evaluation quality, and operational risk.

• Guide the architecture of microservices and shared platforms that orchestrate LLM tasks across offensive workflows.

• Lead architectural transformations when the existing approach cannot support the company’s scale, product ambitions, or safety requirements; document the vision, build the case, and bring engineers and leadership along.

• Ensure the organization can operate and improve these systems over time through strong ownership, incident learning, measurable quality standards, and sustainable technical practices.

What You’ll Bring

• Exceptional Python and software engineering expertise, with deep experience designing systems that are secure, reliable, observable, and operable at scale.

• Deep expertise in offensive security, penetration testing, exploit development, vulnerability research, or a closely related discipline.

• Recognized expertise in AI/LLM and agentic-system security, including the ability to identify novel attack paths and translate them into durable technical strategy.

• Deep command of the OWASP Top 10 for LLM Applications and MITRE ATLAS, combined with the judgment to extend beyond existing frameworks.

• A track record of shipping or shaping high-impact security capabilities, platforms, research programs, or technical standards across multiple teams.

• Demonstrated ability to define long-term technical vision, resolve the company’s hardest ambiguous problems, and drive execution through influence rather than direct authority.

• Company-wide technical judgment: able to make consequential tradeoffs across product value, safety, reliability, cost, speed, and maintainability.

• Proven ability to develop senior technical talent and multiply the mentorship capacity of an engineering organization.

• Self-motivated, highly credible, and deeply engaged with the direction of the AI security industry.

What Sets You Apart

• Experience setting technical direction or architecture across an engineering organization or multiple product areas.

• Industry-level contributions to AI security research through influential publications, conference talks, CVEs, open-source projects, or widely adopted techniques.

• Experience shaping strategy for cloud AI platforms such as AWS Bedrock, AWS Agent Core, Azure OpenAI, or Google Vertex AI.

• Deep experience with agentic architectures, tool-use security, retrieval systems, vector databases, graph databases such as Neo4j, or AI infrastructure security.

• Background in traditional exploit development, vulnerability research, or building offensive security platforms at significant scale.

• CTF experience, particularly in AI/ML-focused challenge categories.

• A record of strengthening a company’s technical credibility, recruiting reach, or market position through external technical leadership.

Travel Required

We are a fully remote company, and this job may require up to 10% of travel to be successful.

Compensation and Values

At Horizon3, we believe that our people are our greatest asset, and our compensation philosophy reflects this core value. We are committed to fostering an environment where all employees feel valued, respected, and rewarded for their contributions. Our compensation structure is designed to be fair, competitive, and transparent, ensuring that every team member is recognized and compensated equitably across roles, levels, and locations.

In accordance with various State’s transparency regulations, we provide the following salary range information for this position:

• Base salary range: $238,000 - $280,000. The exact salary will be determined based on the selected candidate’s location, qualifications, experience, and relevant skills.

• Additional compensation: All full-time roles are eligible for an equity package in the form of stock options.

Perks of Horizon3

• Inclusive Team: We value diversity and promote an inclusive culture where everyone can thrive.

• Growth Opportunities: Be part of a dynamic and growing team with numerous career development opportunities.

• Innovative Culture: Work in a collaborative environment that encourages creativity and out-of-the-box thinking.

• Hybrid & Remote Work: We embrace a mix of remote and hybrid work models depending on role and location, including our Chicago office, where some roles require regular in-office presence.

• Competitive Compensation: We offer competitive salary, equity and benefits. Our benefits include health, vision & dental insurance for you and your family, a flexible vacation policy, and generous parental leave.

You Belong Here

Horizon3 is not just an equal opportunity employer - we are a community that values diversity, equity, and inclusion as fundamental principles of our culture and success. We are dedicated to fostering a workplace where everyone feels welcome and respected, regardless of race, color, religion, sex, national origin, age, disability, veteran status, sexual orientation, gender identity or expression, genetic information, marital status, hair length or any other legally protected status by law.

Our commitment to diversity and inclusion means we strive to attract, develop, and retain a workforce that reflects the varied communities we serve. We believe that diverse perspectives drive innovation and strengthen our ability to create cutting-edge cybersecurity solutions. At Horizon3, every team member is valued and supported in an environment that encourages personal and professional growth.

We welcome candidates from all backgrounds and experiences, and we encourage all qualified individuals to apply. Come be a part of Horizon3, where your unique contributions are recognized, and your potential is limitless.

Other Duties

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.

Application Note

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