Subject Matter Expert

Position: Subject Matter Expert I
About ARSIEM Corporation

At ARSIEM Corporation we are committed to fostering a proven and trusted partnership with our government clients. Weprovide support to multiple agencies across the United States Government. ARSIEMhas an experienced workforce of qualified professionals committed to providing the best possible support.

As demand increases, ARSIEM continues to provide reliable and cutting-edge technical solutions at the best value to our clients.

That means a career packed with opportunities to grow and the ability to have an impact on every client you work with.

ARSIEM is looking for a Senior Detection Engineer. The Senior Detection Engineer develops, validates, deploys, and tunes detection logic supporting proactive threat hunting across federal and critical infrastructure environments. The role combines advanced threat hunting tradecraft, adversary behavior analysis, and detection engineering to identify sophisticated threats, close visibility gaps, and improve detection effectiveness.

The engineer translates threat intelligence, hunt findings, and incident response lessons into reliable behavioral analytics, investigative queries, and automation. This work moves the team beyond individual hunts toward faster, repeatable, and scalable operations. Working across endpoint, network, identity, and cloud telemetry, the engineer selects detection methods based on available evidence and mission requirements. The position serves as the technical bridge between threat hunters, technical delivery teams, system engineers, analytics developers, and data scientists, turning operational findings into validated detections, automation, sensing improvements, and actionable capability requirements.

This position will support one of our Government clients in Arlington, VA.

Responsibilities

• Develop and test hypotheses to uncover persistence, privilege escalation, credential access, lateral movement, command and control, and defense evasion.
• Correlate evidence across data sources and document defensible conclusions.
• Build behavioral analytics, correlation rules, signatures, and queries using endpoint, network, identity, cloud, and application telemetry.
• Target adversary techniques and activity sequences rather than individual indicators of compromise.
• Convert validated hunt methods, incident findings, and exercise results into reusable detections.
• Document each detection’s purpose, data requirements, investigative guidance, assumptions, and known limitations.
• Translate remaining gaps into technical requirements and acceptance criteria, recommend priorities through Threat Hunting governance, and verify that delivered capabilities meet the operational need.
• Test detections against representative malicious and benign activity using historical telemetry, controlled simulations, and purple team exercises.
• Verify intended behavior, evaluate evasion opportunities, and retain test evidence.
• Analyze false positives, false negatives, alert volume, thresholds, exclusions, and environmental baselines.
• Improve detection fidelity and alert context through enrichment and prioritization, while assessing the risk of suppressing legitimate threat activity.
• Assess the availability, reliability, and quality of sensors, tools, and data sources.
• Identify collection, parsing, normalization, and retention gaps and explain their impact on active hunts and production detections.
• Coordinate remediation with infrastructure teams and validate restored coverage.
• Develop and maintain automation for enrichment, query execution, analytical workflows, and detection validation, including SOAR playbooks where applicable.
• Tune data pipelines and queries for speed and responsiveness.
• Build in review, error handling, and recovery procedures.
• Maintain version-controlled content, peer reviews, release criteria, approval records, and rollback procedures.
• Revalidate analytics after platform, schema, environmental, or adversary tradecraft changes.
• Coordinate with hunters, incident responders, intelligence analysts, and platform engineers to integrate detections into investigative and automated workflows.
• Measure validated detection coverage, fidelity, actionable findings, and remaining gaps.
• Communicate the operational significance of technical findings and avoid equating rule counts with effective coverage.
• Partner with analytics developers and data scientists to develop and validate advanced analytics, including machine learning where appropriate.
• Assess operational value, false positives, data…