Principal Information Systems Security Engineer

Agentic Defense Solutions, Inc.; Tysons (VA); On-site; USD 150,000 - 230,000; Full time

Job summary

Agentic Defense Solutions, Inc. is hiring a Principal Information Systems Security Engineer to act as the senior technical authority for security across mission systems at multiple classification levels.

You will own security architecture from concept through accreditation and sustainment, translating policy into buildable requirements and serving as the main technical interface to AO, SCA, and ISSM staff. You will lead the technical direction, defend risk positions in architecture reviews, and

Qualifications

• Active TS/SCI with Full Scope Polygraph.
• 15+ years of relevant security engineering experience.
• 10+ years in a classified environment.
• Ownership of at least three systems through full ATO.
• Deep knowledge of NIST SP 800-53, NIST RMF (SP 800-37), CNSSI 1253, ICD 503, and DISA STIG/SRG.
• Hands-on depth in two or more: Linux hardening, network security, IAM, cloud security, or cryptographic key management.
• Ability to communicate technical risk clearly to government stakeholders and write accreditation documentation.

Responsibilities

• Lead security architecture and design for mission systems across on‑premises enclaves, air‑gapped environments, and cloud regions.
• Own the full RMF/ATO lifecycle including evidence artifacts (SSP, SAR, POA&M) and risk assessments.
• Interface with AO, SCA, ISSM and customer stakeholders; present risk positions and tailoring rationale.
• Perform threat modeling and security reviews; document residual risk and mitigations.
• Audit control implementations against NIST SP 800-53, CNSSI 1253, DISA STIGs; drive automated compliance.
• Lead responses to assessments, vulnerabilities, and incidents; conduct root‑cause analysis and durable fixes.
• Mentor junior ISSEs and engineers; establish reusable patterns and engineering standards.
• Support capture and proposals as a security SME and solution architecture contributor.

Skills

TS/SCI clearance

Full Scope Polygraph

Senior security engineering

Risk communication

Tools

NIST RMF

NIST SP 800-53

CNSSI 1253

DISA STIG/SRG

Job description

Principal Information Systems Security Engineer

This position requires an active TS/SCI clearance with a current Full Scope Polygraph at the time of application. Due to the nature of the work and U.S. Government contractual requirements, applicants must be U.S. citizens and must be able to maintain the required clearance for the duration of employment. Candidates without an active in-scope clearance and polygraph cannot be considered, and we are unable to sponsor clearances for this role.

About the Role

Agentic Defense Solutions, Inc. is seeking a Principal Information Systems Security Engineer to serve as the senior technical authority for security engineering across a portfolio of mission systems operating at multiple classification levels. This is a hands‑on senior individual contributor role: you will own security architecture from concept through accreditation and sustainment, translate policy into buildable engineering requirements, and act as the primary technical interface to the customer's Authorizing Official (AO), Security Control Assessors, and ISSM staff.

You will set the technical direction that other engineers follow. We are looking for someone who can hold their own in an architecture review, defend a risk position to an AO, and still get into the weeds on a STIG finding when it matters.

What You'll Do

• Lead security architecture and design for complex mission systems spanning on‑premises enclaves, air‑gapped environments, and accredited cloud regions.
• Own the full accreditation lifecycle under NIST RMF and ICD 503 — categorization, control selection and tailoring, implementation, assessment support, and ATO sustainment — including authoring and defending body‑of‑evidence artifacts (SSP, SAR, POA&M, risk assessments).
• Serve as the senior technical interface to the AO, SCA, ISSM, and government customer stakeholders; present and negotiate risk positions and control tailoring rationale.
• Perform threat modeling, security architecture reviews, and design trade studies; document residual risk and recommend mitigations that the mission can actually live with.
• Engineer and validate control implementations against NIST SP 800-53, CNSSI 1253, DISA STIGs, and applicable overlays; drive automated compliance validation where possible.
• Lead technical response to assessment findings, vulnerability disclosures, and incidents; conduct root‑cause analysis and drive durable engineering fixes rather than one‑off patches.
• Mentor mid‑ and senior‑level ISSEs, ISSOs, and system engineers; establish reusable patterns, reference architectures, and engineering standards across programs.
• Support capture and proposal efforts as a security subject matter expert, including technical volume authorship and solution architecture for new business.

Required Qualifications

• Active TS/SCI with Full Scope Polygraph .
• 15+ years of relevant experience;
• Minimum 10 years performing information systems security engineering in a classified environment.
• Demonstrated ownership of at least three systems through full ATO, including direct engagement with an AO or SCA.
• Deep working knowledge of NIST SP 800-53, NIST RMF (SP 800-37), CNSSI 1253, ICD 503, and DISA STIG/SRG application.
• Hands‑on engineering depth in at least two of: Linux system hardening, network security architecture, identity and access management, cloud security (AWS/Azure), container orchestration security, or cryptographic key management.
• Proven ability to communicate technical risk clearly to non‑technical government stakeholders and to write accreditation documentation that survives assessment.

About Agentic Defense Solutions Inc

Agentic Defense Solutions exists to solve the real problem in mission‑critical AI: not better models, but the operational trust layer that makes AI governable, auditable, and safe to deploy in high‑consequence environments.

Our Mission

Most people think the challenge in mission‑critical AI is better models. It isn't. The real problem is there is no control plane for how AI reasons, makes decisions, and executes operations in high‑consequence environments.

Agentic Defense Solutions builds the ARIA product family: the operational trust layer for AI where decisions have real‑world impact. From the ARIA Platform foundation to the ARIA Hermes application, we provide the infrastructure that makes AI governable, auditable, and safe to deploy so that warfighters, analysts, operators, and decision‑makers can leverage AI with confidence.

We believe that AI accountability shouldn't be an afterthought. It should be the foundation. ARIA enforces policy, keeps an immutable audit trail, supports human‑in‑the‑loop, and is built for air‑gapped and classified deployment from day one.