The weaponization of AI is driving a paradigm shift in the cyber security industry from proactive to preemptive security: clients must now invest more intelligence and effort in understanding their vulnerabilities before their adversaries do (Open AI). The only way to achieve this is to simulate future attack scenarios at scale, and to run them in high fidelity digital replicas of production environments (Gartner/Forrester). SimSpace serves as the AI Proving Grounds to generate hypersynthetic data which pressure tests controls, tools, teams, and agentic capabilities in full kill chain attacks hidden in realistic environmental traffic and patterns of life.

Founded in 2015 by experts from U.S. Cyber Command and MIT Lincoln Laboratory, the platform was initially conceived to assist in Offensive Cyber Operations (OCO), to quickly replicate target environments to conduct mission rehearsal of human operators and their tools to deny (disrupt, degrade, destroy) or deceive (manipulate or exfiltrate data) adversaries. The company has since expanded to serve over a dozen allied governments in OCO/DCO as well as critical infrastructure enterprises around the world. The company is actively investing in the Americas, Asia Pacific, Europe and the Middle East through direct sales and channel partners. SimSpace has launched the AI Proving Grounds Consortium, leading the revolution by creating an open platform for the InfoSec ecosystem to train, validate and operationalize their agentic capabilities before committing to production.

Why join SimSpace?

We are a team united by a shared purpose and four core values: Serve to Protect, Acquire Understanding, Teamwork without Borders, and Operate as Innovators. We value candid, constructive feedback and create opportunities for personal, professional, and financial growth. Our vision, “Defend the Free World,” drives our mission: “Defeat Any Adversary in Any Cyber Terrain at Machine Speed.”

How Do We Work?

We listen to customers and colleagues, challenge assumptions, and turn ideas into meaningful results. We expect everyone to embrace emerging technologies, simplify and automate work, and use AI to learn, solve problems, and help deliver quality with speed. We apply human judgment and take responsibility for outcomes. Whether remote or office-based, we collaborate across teams and time zones.

We invite you to apply today!

We are looking for a Senior Software Engineer, Greyspace, to design and develop a realistic, simulated internet for SimSpace cyber ranges. You will help build the services, networking, and operator workflows that make training environments believable, repeatable, and safely contained. The ideal candidate brings deep experience building distributed software systems, strong networking fundamentals, and the ability to turn ambiguous requirements into working software across team boundaries.

In this hands-on engineering role, you'll contribute to Greyspace's architecture and implementation with Product, Security, and engineering partners. You will write and review code, prove architectural decisions through working increments, and take services from early implementations to reliable operation. The focus is on building reusable simulated services with clear isolation boundaries and integrating them into the SimSpace platform. Specifically, this position will be responsible for:

Greyspace service architecture, APIs, and orchestration for configuring and managing simulated internet environments

Realistic network and application behavior, including DNS, TLS, web, and mail services

Reusable services and content with isolated per-range configuration, identities, and mutable state

Platform and range integrations, operator workflows, automated validation, and operational readiness

What will you be doing as a Senior Software Engineer, Greyspace at SimSpace?

Own technical design and implementation for Greyspace services, defining service boundaries, data ownership, API contracts, and failure behavior in collaboration with technical leads and partner teams.