Senior System Software Engineer

Senior System Software Engineer

CounterCraft

San Sebastian or Remote, Spain

We’re looking for a Senior System Software Engineer who knows how systems work from the inside out - someone who lives at the intersection of OS internals, secure coding, and real-world performance at scale.

About the Role

You’ll be part of the Security Engineering team, building the cross-platform monitoring agent that powers our adversary-facing tech. It’s the kind of code that runs deep in the system - and makes a real difference in the fight against sophisticated cyber threats.

What You’ll Do

• Build and maintain low-level system software on Linux and Windows.
• Drive architecture and design decisions across both platforms.
• Provide technical leadership for new features and long-term roadmap planning.
• Maintain and improve our CI pipeline and test suites.
• Support the Ops team in understanding and resolving issues in live environments.
• Help shape a team culture grounded in technical excellence and software resilience.

What We’re Looking For

• 5+ years of experience in system-level software engineering.
• Deep expertise in C/C++.
• Strong understanding of Windows & Linux internals.
• Solid grasp of multi-threading, performance tuning, and concurrency.
• Proven track record designing and shipping multi-platform solutions.
• Experience in the security or threat intelligence space.
• Familiar with Python and scripting for system tasks.
• Strong understanding of secure coding practices and software lifecycle.

Bonus Points For

• Hands-on with eBPF (or curious to go deep there).
• Experience contributing to open source, especially kernel-related projects.
• Familiarity with stealth, monitoring, or anti-forensic techniques.

Who You Are

• Technically driven, with an eye for elegant and practical solutions.
• Comfortable owning complex components end-to-end.
• Clear communicator who can collaborate with cross-functional teams.
• Fluent in English.
• Always learning. Always improving.