The Microsoft Security Defender for Office (MDO) Team delivers cloud-based email and messaging protection that safeguards customers from advanced threats—including malware, phishing, fraud, and spam—across Microsoft email and Teams workloads. MDO also provides powerful investigation, threat hunting, and remediation capabilities, enabling security teams to quickly identify, prioritize, and respond to threats at scale.

Security is a top priority at Microsoft, and the Defender for Office team operates at the forefront of this mission. We focus on detecting malicious activity, responding rapidly, and neutralizing threats before they impact customers.

We are seeking a Principal Software Engineer to join our Foundations Organization to help build the next generation of services that will power MDO into the future. In this role, you will serve as a security architect and advocate, shaping a secure-by-design platform and driving a security-first mindset across the organization. You will lead architectural decisions, influence culture, and collaborate across geographies and engineering teams to deliver resilient, next-generation security solutions.

• Lead the design and implementation of authentication and security foundations that protect Microsoft Defender for Office against advanced threats at cloud scale
• Architect and deliver secure‑by‑design, highly scalable services, ensuring solutions meet Microsoft security standards while anticipating future threat models and platform evolution
• Operate effectively in ambiguous, fast‑moving environments, providing technical clarity and direction where requirements and threat landscapes evolve rapidly
• Collaborate deeply with peer engineers and partner teams across MDO, MSEC, and Substrate to design durable, end‑to‑end security solutions that balance protection, performance, and customer experience
• Serve as a security leader and advocate, championing a security‑first mindset through architecture reviews, design guidance, and technical leadership across teams and geographies
• Influence platform‑level decisions by identifying systemic security risks, defining mitigations, and driving alignment on long‑term architectural investments
• Mentor and raise the security engineering bar across the organization by setting best practices, reviewing critical designs, and modeling resilient security engineering discipline
• Partner with stakeholders to ensure solutions meet customer security expectations, compliance requirements, and operational excellence at global scale

Microsoft is an equal opportunity employer. All qualified applicants will receive consideration for employment without regard to age, ancestry, citizenship, color, family or medical care leave, gender identity or expression, genetic information, immigration status, marital status, medical condition, national origin, physical or mental disability, political affiliation, protected veteran or military status, race, ethnicity, religion, sex (including pregnancy), sexual orientation, or any other characteristic protected by applicable local laws, regulations and ordinances. If you need assistance with religious accommodations and/or a reasonable accommodation due to a disability during the application process, read more about requesting accommodations.