Senior Information System Security Engineer

Senior Information System Security Engineer based in Warrenton, VA, focusing on Trellix ePO and ACAS management, RMF/ATO support, and secure-by-design practices across the SDLC for mission-critical assets.

Responsibilities

• Oversee the Trellix ecosystem across Windows and Linux: design, configure, and maintain the ePO server, Trellix Agent, DLP, HIPS, Policy Auditor, ABM, and VSE.
• Create and deploy endpoint security policies for ENS modules (Threat Prevention, Firewall, Web Control) aligned to DISA STIGs and organizational needs.
• Develop custom signatures, rules, and exceptions to address zero-day threats and operational requirements.
• Validate custom exceptions to ensure mission-critical processes remain operational while preserving compliance.
• Design enterprise-wide vulnerability scanning strategies and manage Security Centers and Nessus scanner deployment.
• Serve as the final escalation point for complex scan issues, credentialing problems, and system communication failures.
• Configure automated compliance reporting to continuous monitoring systems and risk-scoring repositories.
• Integrate Trellix and ACAS with Splunk, XSOAR, and ServiceNow to automate workflows and enhance incident response.
• Provide authoritative RMF recommendations and ACAS artifacts to support A&A processes and RMF packages for Authority to Operate (ATO).
• Lead the maintenance and scalability of test, development, and operational environments in collaboration with Network and DevSecOps teams to improve resilience.
• Deliver Tier 1–3 maintenance and incident response for the full cybersecurity portfolio (ACAS, Trellix, Splunk, XSOAR).
• Maintain deep understanding of DISA STIGs, NIST 800-53, and the RMF framework.

Requirements

• Active TS/SCI clearance (or TS with SCI eligibility) and ability to obtain SCI.
• Experience with Nessus/ACAS and Trellix administration.
• Experience operating in a Splunk clustered environment.
• 40-hour work week, typically Monday through Friday, with overtime as needed during critical periods.
• Willingness to travel 5–10 percent, primarily within 75 miles.
• Proficiency with MS Office applications: Excel, Word, Outlook, SharePoint, Project, Visio.
• Exceptional attention to detail; strong verbal and written communication; solid critical thinking, organization, time management, and problem-solving skills.
• Ability to work independently and as part of a team in a dynamic environment.

Technologies

• Trellix (ePO), Trellix Agent, DLP, HIPS, Policy Auditor, ABM, VSE
• Nessus, ACAS
• Splunk, XSOAR, ServiceNow
• Windows, Linux
• MS Office, Excel, Word, Outlook, SharePoint, Project, Visio

Benefits

• 401(k)
• 401(k) matching
• Dental insurance
• Employee assistance program
• Employee discount
• Flexible schedule
• Flexible spending account
• Health insurance
• Health savings account
• Life insurance
• Paid time off
• Parental leave
• Professional development assistance
• Referral program
• Retirement plan
• Tution reimbursement
• Vision insurance

Other Responsibilities

• Safety: Maintain a safe work environment, complete required training, participate in emergency response tasks, and serve on safety committees as applicable.
• Quality: Adhere to the Amentum Quality Policy and related Quality System documents; understand Quality Management and Customer Satisfaction responsibilities.
• Procedure Compliance: Read, understand, and implement general and specific operational, safety, quality and environmental requirements of all plans, procedures, and policies relevant to the role.

Education

• Bachelor's degree in Cyber and/or Engineering (Required)

Experience

• Trellix Administration: 5 years (Required)
• Splunk: 6 years (Required)
• ACAS/Nessus: 8 years (Required)

Licenses & Certifications

• TS/SCI (Required)
• IAT Level II (Required)

Location

Warrenton, VA 20186; Onsite, in-person work required.