Information System Security Engineer with Security Clearance

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 to:

• Assist with or lead the design and integration of technical security controls into system hardware, software, and networking architectures throughout the SDLC
• Work within a technical security engineering team responsible for implementing and maintaining compliant security architectures across complex platforms
• Support RMF execution and system categorization by defining authorization boundaries with network diagrams, hardware/software inventories, data flow documentation, and cryptographic mapping
• Perform hands-on configuration, hardening, log analysis, and remediation on Linux and RTOS environments while enforcing DISA STIGs via automated scripting
• Operate, configure, and maintain Nessus vulnerability scanners and collaborating with ISSOs to analyze scan outputs and determine remediation pathways
• Deploy, configure, and troubleshoot Trellix endpoint security tools across host endpoints to enforce strict media/device control policies and host-based defenses
• Support and maintain enterprise log ingestion and SIEM platforms such as Splunk or Elastic (ELK) to support centralized auditing and continuous monitoring
• Maintain accurate RMF artifacts in eMASS, including the System Security Plan (SSP), POA&M, and supporting technical evidence to support Authorizing Official (AO) decisions Minimum Qualifications:
• Bachelor'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 experience
• 2+ years of hands-on experience configuring, hardening, or troubleshooting Linux operating systems, with exposure to RTOS (e.g., QNX, VxWorks) or Windows environments
• Active DoD 8570/8140 IAT Level II certification, e.g., CompTIA Security+ CE, CySA+, SecurityX, CISSP
• Hands-on experience or working knowledge of Nessus vulnerability scanners and Trellix endpoint security tools
• Experience or training with eMASS
• Familiarity with scripting languages (Bash, Python, or PowerShell) for basic task automation, configuration management, or compliance checking

Preferred Qualifications

• Hands-on experience installing, configuring, or operating Splunk, Elasticsearch/Kibana (ELK), or another enterprise log analytics platform
• Understanding of PL2 vs. PL3 security baselines, trust boundaries, and segmentation concepts
• Active industry certifications such as CompTIA Linux+, CGRC, or IAT Level III SecurityX (CASP+), or CISSP
• Experience integrating security into the SDLC or utilizing configuration management tools (Ansible, Puppet, Chef) for STIG automation Clearance Requirements:
• Must have a current or active Top Secret security clearance Physical Requirements:
• Must be able to remain in a stationary position 50% of the time
• Needs 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