Subject Matter Expert I

Arsiem•Arlington, VA

2d•Onsite

About The Position

ARSIEM Corporation is seeking a Senior Detection Engineer to support a government client in Arlington, Virginia. The role develops, validates, deploys, and tunes detection logic for proactive threat hunting across federal and critical infrastructure environments. It combines threat hunting, adversary behavior analysis, and detection engineering to identify sophisticated threats, close visibility gaps, and improve detection effectiveness. The engineer turns threat intelligence, hunt findings, and incident response lessons into behavioral analytics, investigative queries, and automation that support repeatable, scalable operations. Working across endpoint, network, identity, cloud, and application telemetry, the engineer selects detection methods based on available evidence and mission requirements. The role connects threat hunters with technical delivery teams, system engineers, analytics developers, and data scientists by translating operational findings into validated detections, automation, sensing improvements, and actionable capability requirements. It also provides technical leadership for vulnerability management and threat hunting activities, and helps develop detection engineering competencies, training, and practical assessments.

Requirements

Bachelor's degree in Engineering, Computer Science, Cybersecurity, Information Systems, or a related field.
10 or more years of directly relevant experience.
Senior-level experience in threat hunting, detection engineering, incident response, or closely related defensive cyber operations, including independent ownership of production detection content.
Strong command of hypothesis development, adversary behavior analysis, iterative investigation, and evidence-based conclusions.
Ability to develop, test, deploy, and tune production detections, explain their limitations, and assess the effects of exclusions and suppression.
Advanced proficiency in one or more security query languages, such as KQL, SPL, EQL, ES|QL, or vendor-specific EDR languages, and ability to adapt and optimize logic across platforms.
Experience analyzing process execution, command lines, process ancestry, authentication, persistence mechanisms, network connections, and related enterprise telemetry.
Understanding of Windows and Linux internals, enterprise networking, identity systems, cloud telemetry, and sophisticated adversary tradecraft.
Practical experience mapping detections to MITRE ATT&CK and explaining the telemetry, test evidence, and limitations behind coverage claims.
Proficiency in Python and PowerShell, or comparable languages, for analysis, enrichment, testing, and automation.
Ability to document detection intent, logic, validation results, investigation steps, and tuning decisions clearly.
Experience translating operational findings into engineering requirements and acceptance criteria, validating sensing effectiveness, and coordinating improvements across hunt analysts and delivery teams.
Active TS/SCI clearance and ability to obtain Department of Homeland Security (DHS) Entry on Duty (EOD) Suitability.

Nice To Haves

Master's degree.
Experience with CrowdStrike Falcon, Microsoft Defender, Cortex XDR, SentinelOne, Elastic, Splunk, or comparable platforms.
Experience with portable detection content such as Sigma.
Experience with detection-as-code and automated testing.
SIEM data onboarding and pipeline tuning experience.
Experience with adversary emulation and cyber exercise development.
Federal civilian or critical infrastructure cyber operations experience.
Experience maintaining detection engineering competencies, Job Qualification Requirements, training scenarios, and practical assessments.
GIAC Certified Detection Analyst (GCDA).
GIAC Certified Forensic Analyst (GCFA).
GIAC Defending Advanced Threats (GDAT).
GIAC Certified Intrusion Analyst (GCIA).
GIAC Certified Incident Handler (GCIH).
GIAC Cyber Threat Intelligence (GCTI).
Microsoft Certified: Security Operations Analyst Associate (SC-200).
Certified Information Systems Security Professional (CISSP).

Responsibilities

Develop and test hypotheses to uncover adversary activity, correlate evidence across data sources, and document defensible conclusions.
Build behavioral analytics, correlation rules, signatures, and queries that target adversary techniques and activity sequences across endpoint, network, identity, cloud, and application telemetry.
Convert validated hunt methods, incident findings, and exercise results into reusable detections, documenting their purpose, data requirements, investigative guidance, assumptions, and limitations.
Translate capability gaps into technical requirements and acceptance criteria, recommend priorities through Threat Hunting governance, and verify delivered capabilities meet operational needs.
Test detections against representative malicious and benign activity using historical telemetry, controlled simulations, and purple team exercises; verify behavior, assess evasion opportunities, and retain test evidence.
Analyze false positives, false negatives, alert volume, thresholds, exclusions, and environmental baselines; improve detection fidelity and alert context while assessing suppression risks.
Assess sensor, tool, and data-source availability, reliability, and quality; identify collection, parsing, normalization, and retention gaps; coordinate remediation and validate restored coverage.
Develop and maintain automation for enrichment, query execution, analytical workflows, and detection validation, including SOAR playbooks where applicable; tune pipelines and queries and 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.
Partner with analytics developers and data scientists to develop and validate advanced analytics, including machine learning where appropriate, and assess operational value, false positives, data dependencies, and limitations.
Provide technical leadership supporting the section focal point for vulnerability management and threat hunting activities under applicable authorities.
Develop exercise scenarios and expected detection outcomes, assess sensing failures, and track corrective actions.
Evaluate new tools, data sources, and analytical methods against mission gaps; document test results, operational limitations, and adoption recommendations.
Review analytical work, mentor analysts, and set standards for query development, documentation, testing, deployment, and tuning.
Develop and maintain detection engineering competencies, Job Qualification Requirements, training scenarios, and practical assessments in coordination with section leadership.