Subject Matter Expert I

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 dependencies, and analytical limitations.
• Provide technical leadership supporting the section focal point for vulnerability management (VM) and threat hunting (TH) activities under applicable authorities. 
• Develop exercises cenarios and expected detection outcomes, assess sensing failures, and track corrective actions.
• Evaluate new tools, data sources, and analytical methods against identified 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 (JQRs), training scenarios, and practical assessments in coordination with section leadership.

Minimum Qualifications

• Bachelor's degree in Engineering, Computer Science, Cybersecurity, Information Systems, or related field (Master's Degree preferred)
• 10+ years of directly relevant experience
• Demonstrated 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.
• Proven 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 (KQL, SPL, EQL, ES|QL, or vendor-specific EDR languages), with the 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 clearly document detection intent, logic, validation results, investigation steps, and tuning decisions.
• Experience translating operational findings into engineering requirements and acceptance criteria, validating sensing effectiveness, and coordinating improvements across hunt analysts and delivery teams.

Preferred Qualifications

• 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 with 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)