Agentic Offensive AI Engineer

Get to Know Us

Horizon3.ai is a fast-growing, remote cybersecurity company dedicated to the mission of enabling organizations to proactively find and 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 ITOps/SecOps teams, consulting pentesters, and MSSPs and MSPs. 

We are a fusion of former U.S. Special Operations cyber operators, startup engineers, and formerly frustrated cybersecurity practitioners. We're committed to helping solve our common security problems: ineffective security tools, 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.

Overview
Join Horizon3 to help pioneer AI Offensive Security (AI OffSec)—where machine learning and cybersecurity collide. We’re seeking junior engineers with a strong AI/ML foundation—especially those eager to explore reinforcement learning (RL) and modern model-tuning methods—to build intelligent agents that probe networks, discover vulnerabilities, and emulate real adversaries. You’ll help design, train, and test AI systems that continuously learn to think and act like attackers.

Essential Functions

• Develop AI systems for vulnerability detection and autonomous security testing

• Design and train reinforcement-learning and fine-tuning workflows (e.g., PPO, LoRA/QLoRA) to improve automated security agents

• Automate security testing pipelines with Python and modern ML frameworks

• Contribute to feature development from concept through deployment, including model evaluation and experiment tracking

• Identify and document vulnerabilities in AI-native applications and LLM workflows

• Research emerging AI security threats, prompt-injection tactics, and adversarial ML

• Document findings and help build a technical knowledge base
  

Core Competencies / Requirements

• Bachelor’s degree in Computer Science, Machine Learning, Artificial Intelligence, Data Science, Software Engineering, Mathematics, Statistics, or a related field

• Strong Python skills and comfort with data-science libraries (NumPy, pandas, scikit-learn)

• Foundational knowledge of AI/ML concepts and frameworks (PyTorch, TensorFlow, or JAX)

• Exposure to reinforcement learning or similar methods (deep Q-learning, PPO) through coursework, labs, or projects

• Understanding of model training life cycle: data prep, feature engineering, and evaluation

• Experience with Linux environments and Git version control

• Interest in cybersecurity and ethical hacking

• Strong problem-solving and clear communication skills

• Must be located in or willing to relocate to the Indianapolis metropolitan area
  

Desired / Nice to Have

• Hands-on projects fine-tuning LLMs or training LoRA/QLoRA adapters

• Experience with vector databases or retrieval-augmented generation (RAG)

• Familiarity with AI security topics (model inversion, adversarial attacks)

• Internship or academic work in reinforcement learning or autonomous agents

• Contributions to open-source RL or adversarial-ML projects

• Experience with Docker and containerized ML ops (Docker/Kubernetes)

• Experience with cloud platforms (AWS, Azure, or GCP)

• Security certifications (Security+, etc.) or active pursuit of them

• Participation in CTF platforms (Hack The Box, TryHackMe, etc.) or AI/ML competitions (Kaggle)
  

What We Offer

• Deep Mentorship: Work side-by-side with experienced engineers to master real-world AI security pipelines

• Career Growth: Opportunity to become a core technical leader as our AI offensive security stack expands

• Hybrid Flexibility: 2–3 days a week in our Indianapolis office with flexible remote options

• Competitive Entry-Level Compensation: Full benefits including health, vision, and dental
  

Ideal Mindset

• Eager to learn and grow in both AI and cybersecurity

• Self-motivated, detail-oriented, and collaborative

• Curious “hacker mindset” with a drive to experiment and break things safely

Citizenship/Clearance

• US Citizen or GreenCard Holder

Perks of Horizon3.ai

• 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.

• Remote Work: We are a 100% remote company. Enjoy the convenience and work-life balance that comes with remote work. 

• 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.

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.

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

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, 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.