Senior Attack Engineer, External

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're looking for a Senior Attack Engineer to drive key workstreams within our external attack capabilities in NodeZero, our autonomous pentesting platform.

For most organizations, the external attack surface is where a breach begins. Customers need NodeZero to find the forgotten host, exposed credential, or misconfigured service, and prove how far each weakness leads. The surface is large and messy. It spans domains, certificates, cloud assets, code repositories, leaked data, identities, SaaS tenants, and the relationships connecting all of it. Much of it is unstructured, inconsistent, and hard to reason about in code. Attackers are also getting faster at finding and chaining these weaknesses together.

This is a high-impact role. You'll independently develop complex workstreams within our external attack domain: contributing to the research and content roadmap, building deep expertise the team relies on, and helping raise the bar for the engineers building alongside you.

This is not consulting or manual pentesting. The goal is to turn the manual recon and multi-step attack work that skilled operators do by hand into safe, reliable, repeatable workflows that run autonomously against some of the largest external attack surfaces in the world.

What You’ll Do

• Design, build, and maintain highly scalable reconnaissance workflows that discover, enumerate, and fingerprint external-facing assets and services in production-grade Python.

• Research, explore, and parse large volumes of external-facing data, including unstructured and inconsistent sources, and turn it into accurate, actionable information.

• Develop robust approaches to data that is hard to reason about in code, such as free-form banners, web content, documents, and error output, and build parsing and enrichment that holds up across the long tail of real environments.

• Collect, store, and connect high volumes of information, and extend our attack-path modeling and graph data model to represent new identity, privilege, and relationship paths.

• Traverse identity relationships across the external surface, such as accounts, tenants, SSO and federation, exposed credentials, and third-party services, to find paths from exposure to compromise.

• Automate multi-step attack workflows that chain discovery, credential access, initial access, and post-exploitation into complete, safely proven attack paths.

• Research emerging external tradecraft and turn it into production attack content, with an emphasis on techniques that still succeed against hardened, well-monitored targets.

• Stand up and maintain representative test environments to validate, demonstrate, and regression-test attack scenarios.

• Build for production safety and scale: respect target and customer environments, rate limits, and scope while running across very large attack surfaces.

• Contribute to priorities and the coverage roadmap based on real customer environments, threat intelligence, and emerging techniques.

• Mentor teammates and proactively support their growth, and help define team standards for code quality, research rigor, and operational safety.

• Collaborate cross-functionally with engineers, product managers, and customer-facing teams, and author internal documentation and external research and blog posts.

What You’ll Bring

• Deep, hands-on offensive experience against external attack surfaces, from reconnaissance through initial access and post-exploitation.

• 5+ years of hands-on experience in offensive security, security research, and/or security-focused software engineering, with recent work building and shipping offensive tooling.

• Demonstrated experience building reconnaissance and discovery systems that run at scale, not just one-off scripts.

• Strong skill at researching and parsing large amounts of messy, unstructured external data and turning it into usable, trustworthy information.

• Experience collecting, storing, and connecting high volumes of data, and reasoning about it as relationships, such as identities, assets, and trust.

• Command of identity-focused tradecraft: credential access, password and token attacks, SSO and federation weaknesses, and moving among identities, tenants, and services.

• Experience automating multi-step attack workflows end to end.

• Strong software engineering fundamentals with Python, and a track record of shipping and maintaining production-quality code, not just scripts and proofs of concept.

• Ability to independently research unfamiliar systems and technologies and rapidly build deep, practical expertise.

• Strong written and verbal communication, including clear technical documentation.

• A passion for building products, not just finding vulnerabilities.

What Sets You Apart

• OSCP (or OSEP, CRTO, or equivalent offensive certifications).

• Experience with large-scale internet data sources and tooling, such as certificate transparency, passive DNS, and internet-wide scanning.

• Experience with cloud, SaaS, and hybrid identity attack surfaces (Entra ID, Okta, AWS, and similar), including on-prem to cloud pivots.

• Experience with external to internal pivoting and how perimeter footholds lead into additional access.

• Experience with graph databases and attack-path analysis, and with data lake or high-volume data storage and processing.

• Experience developing or contributing to offensive or recon tooling

• Public contributions to the field: open-source tools, technical blog posts, conference talks, or published CVEs.

• Experience building production-safe autonomous or automated offensive tooling.

Travel Required

We are a fully remote company, and this job may require up to 5% 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: $206,278 - $242,680 annually. 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.ai

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

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