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

• Aligned with this goal, Halcyon is searching for a security researcher to contribute to a number of strategic research initiatives to develop Halcyon’s product and services catalogue
• Halcyon’s primary focus for this role is to analyze ransomware samples and threat actor tools to gain insights for future product features, threat actor insights, and assist in the validation of our current capabilities
• The ideal candidate will be a proficient reverse engineer with experience in analyzing malware, have a strong understanding of cryptography used in ransomware, and the ability to develop tools to augment existing capabilities
• 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)