Senior Product Security Engineer, Halcyon

• 5+ years in product security or endpoint-focused consulting, with hands-on testing of Windows-based agents or EDR/AV products
• Experience building fuzzers or integrating existing fuzzing frameworks for native code
• Experience and capability in building automated test harnesses from the ground up
• Strong Windows OS internals knowledge, especially user-mode hooking and Win32 API behaviors
• Proficient in C/C++ and Python, with solid experience calling with Windows APIs
• Experience reviewing and validating security findings
• Comfortable researching and suggesting security features end-to-end and creating technical content

Desirable

• Halcyon’s goal is to deliver an anti-ransomware solution that breaks new ground in what a security product can achieve
• Aligned with this mission, we’re hiring a Senior Product Security Engineer to ensure our most innovative defenses make it into every release
• These cutting-edge capabilities will keep our customers ahead in the fight against ransomware
• Endpoint Hardening & Testing
• Design and implement security test harnesses from scratch to simulate real-world ransomware behavior
• Develop and integrate fuzzers (libFuzzer, AFL/WinAFL, or custom tools) for automated crash and vulnerability discovery
• Build user-mode hooking instrumentation and explore EDR bypass techniques to exercise agent internals
• Vulnerability Research & Triage
• Triage, reproduce, and analyze security findings against our agent and libraries
• Perform root-cause analysis on crashes or logic flaws; build minimal PoC exploits or reproducer cases
• Platform Expertise
• Deep understanding of Windows internals (ring transitions, memory management, Win32 API) with focus on user-mode security hooks
• Collaborate on driver-level or API-level integrations when necessary (no kernel-driver dev required)
• Play a critical role in developing cutting-edge ransomware protections and security features that will have a real-world impact
• Work alongside highly skilled security researchers and engineering teams building next-generation security solutions
• Have the opportunity to shape the process by which security innovations transition from research into real-world implementations
• Be part of a company deeply committed to stopping ransomware and protecting customers