Information System Security Engineer

MANTECH seeks a motivated, career and customer-oriented Information Systems Security Engineer to join our team in Chantilly, VA. This position will be onsite. This role can optionally be in San Diego, CA.The Information Systems Security Engineer (ISSE) will support Risk Management Framework (RMF), security engineering, and cybersecurity lifecycle activities. This role focuses on security control design and implementation, system hardening, technical remediation, continuous monitoring, and security stack operations, with an emphasis on Linux systems and real-time operating systems (RTOS), alongside supporting knowledge of Windows environments.Responsibilities Include But Are Not Limited ToAssist with or lead the design and integration of technical security controls into system hardware, software, and networking architectures throughout the SDLCWork within a technical security engineering team responsible for implementing and maintaining compliant security architectures across complex platformsSupport RMF execution and system categorization by defining authorization boundaries with network diagrams, hardware/software inventories, data flow documentation, and cryptographic mappingPerform hands-on configuration, hardening, log analysis, and remediation on Linux and RTOS environments while enforcing DISA STIGs via automated scriptingOperate, configure, and maintain Nessus vulnerability scanners and collaborating with ISSOs to analyze scan outputs and determine remediation pathwaysDeploy, configure, and troubleshoot Trellix endpoint security tools across host endpoints to enforce strict media/device control policies and host-based defensesSupport and maintain enterprise log ingestion and SIEM platforms such as Splunk or Elastic (ELK) to support centralized auditing and continuous monitoringMaintain accurate RMF artifacts in eMASS, including the System Security Plan (SSP), POA&M, and supporting technical evidence to support Authorizing Official (AO) decisionsMinimum QualificationsBachelor’s degree in IT, Computer Science, Cybersecurity, Computer Engineering, or related field with 2+ years of relevant cybersecurity, system administration or RMF experience; OR High School Diploma/GED with 6+ years of cybersecurity engineering, system administration, or RMF experience2+ years of hands-on experience configuring, hardening, or troubleshooting Linux operating systems, with exposure to RTOS (e.g., QNX, VxWorks) or Windows environmentsActive DoD 8570/8140 IAT Level II certification, e.g., CompTIA Security+ CE, CySA+, SecurityX, CISSPHands-on experience or working knowledge of Nessus vulnerability scanners and Trellix endpoint security toolsExperience or training with eMASS Familiarity with scripting languages (Bash, Python, or PowerShell) for basic task automation, configuration management, or compliance checkingPreferred QualificationsHands-on experience installing, configuring, or operating Splunk, Elasticsearch/Kibana (ELK), or another enterprise log analytics platformUnderstanding of PL2 vs. PL3 security baselines, trust boundaries, and segmentation conceptsActive industry certifications such as CompTIA Linux+, CGRC, or IAT Level III SecurityX (CASP+), or CISSPExperience integrating security into the SDLC or utilizing configuration management tools (Ansible, Puppet, Chef) for STIG automationClearance RequirementsMust have a current or active Top Secret security clearancePhysical RequirementsMust be able to remain in a stationary position 50% of the timeNeeds to occasionally move about inside the office to access file cabinets, office machinery, etc.Frequently communicates with co-workers, management, and customers, and must be able to exchange accurate information in these situations