Horizon3 hiring an Applied AI Engineer, Autonomous Defense for a remote position in the US. This role suits a machine learning professional interested in building closed-loop defense agents that map attack paths to security control changes.
Role Overview
Horizon3 is looking for an AI Researcher to build the agents that turn offensive knowledge into defensive action. The position involves designing reasoning systems that operate inside customer tenants and modify production security controls safely at enterprise scale.
Key Responsibilities
Build reasoning systems mapping proven attack paths and exploitation telemetry to specific, applicable control changes ranked by effectiveness.
Turn pentest data into training and evaluation data by extracting the signal of why attacks succeed or fail.
Design and run counterfactual experiments in representative test environments to test attack chain breaks and operational costs.
Design the reasoning layer over heterogeneous control planes so agents work across vendor APIs without hardcoded playbooks.
Design safety architecture for autonomous change including dry-run, simulation, blast-radius classification, approval gates, staged rollout, rollback, and audit trails.
Collaborate with attack and detection engineers to define target agent behavior and diagnose failure modes.
Own problems end to end in a 0 to 1 environment with ambiguous requirements and high reliability standards.
Requirements
Strong machine learning engineering experience building, evaluating, and deploying production AI systems with deep learning, transformer models, and PyTorch.
Hands-on experience with post-training large language models or designing agentic systems with tool use, planning, and long-horizon execution.
Track record of building evaluation systems for open-ended tasks without clean labels.
Experience reasoning over structured, heterogeneous, messy real-world data like configurations, graphs, logs, and policy documents.
Software engineering fundamentals and a track record of shipping and maintaining production-quality code in Python.
Experience with data pipelines, distributed systems, and cloud infrastructure, preferably AWS.
Ability to work across model behavior, APIs, and infrastructure while collaborating with cross-functional teams.
Ability to independently research unfamiliar systems and rapidly become the team expert.
Strong written and verbal communication skills with technical documentation experience.
Master's degree in Computer Science, Machine Learning, or related field plus 4 years of professional engineering experience, or equivalent practical experience.
Nice to Have
Background in detection engineering, purple teaming, security engineering, offensive security, or incident response.
Hands-on familiarity with security control planes and APIs such as EDR, firewalls, identity and conditional access, SIEM, cloud IAM, WAF, MDM, and GPO.
Experience with causal or counterfactual inference, graph reasoning, planning, and search over large state spaces including Neo4j and attack-path analysis.
Experience building automation that takes write actions in production systems with safety and change-management machinery.
Experience with adversarial robustness or prompt injection.
Experience integrating ML into production, multi-tenant SaaS, or customer-controlled and air-gapped environments.
Skills and Tools
PyTorch
Python
AWS
Neo4j
Large Language Models
Salary and Benefits
Salary range of $313,000 to $369,000
Competitive compensation including salary, equity, and benefits
Health, vision, and dental insurance for employees and families
Flexible vacation policy
Generous parental leave
Inclusive team, growth opportunities, and hybrid or remote work models
About the Company
Horizon3 is a fast-growing, remote cybersecurity company that enables organizations to proactively find, fix, and verify exploitable attack vectors. Its flagship NodeZero platform delivers production-safe autonomous pentests across internal, external, cloud, and hybrid cloud environments for organizations ranging from educational institutions to government agencies and Global 100 enterprises.
How to Apply
Apply on the official company careers page.
