In support of a challenging, critical, and rewarding program that provides integrated voice, video, and data services throughout the Information Technology lifecycle, Amentum is seeking Senior Information System Security Engineer (ISSE) to serve as a subject matter expert in the design, implementation, and optimization of enterprise security toolsets. The successful candidate will lead the engineering efforts for the Trellix (ePO) ecosystem and the ACAS (Nessus) suite, ensuring mission-critical assets remain secure, compliant, and resilient. This role requires a blend of high-level security architecture, hands-on troubleshooting, and the ability to drive secure-by-design principles across the System Development Life Cycle (SDLC). You must be a critical thinker, have a strong work ethic, and be able to work independently or as a member of a team in a dynamic environment. We value candidates who are detail-oriented while also being able to think and react quickly to emerging and unique p...