Principal Security Engineer

Block; San Francisco (CA); On-site; USD 150,000 - 200,000; Full time

Job summary

Block is hiring a Principal Security Engineer focused on Software Security Engineering in San Francisco. This role involves delivering innovative solutions to security challenges and defining technical strategies for software security.

You will lead critical initiatives, mentor engineers, and work closely with the CISO to enhance security across Block's services. A minimum of 10 years of experience in software development and a strong focus on security practices are required.

Qualifications

• 10+ years of experience in software development and critical services.
• Proven record of implementing security practices.
• Mastery of system design and architectural concepts.

Responsibilities

• Deliver innovative software solutions to security challenges.
• Define technical strategy and guide architectural decisions.
• Lead development of common security solutions across business units.
• Ensure engineering excellence for critical security systems.
• Mentor engineers on security practices and system design.

Skills

Technical leadership

Software development

Security practices

System design and architecture

Collaboration skills

Job description

Block is one company built from many blocks, all united by the same purpose of economic empowerment. The blocks that form our foundational teams — People, Finance, Counsel, Hardware, Information Security, Platform Infrastructure Engineering, and more — provide support and guidance at the corporate level. They work across business groups and around the globe, spanning time zones and disciplines to develop inclusive People policies, forecast finances, give legal counsel, safeguard systems, nurture new initiatives, and more. Every challenge creates possibilities, and we need different perspectives to see them all. Bring yours to Block.

The Role

As a Principal Security Engineer focused on Software Security Engineering at Block, you will be a technical leader reporting to the CISO responsible for setting the bar for security excellence and driving the creation of innovative, world‑class software solutions to complex security problems. You will work across Engineering and Information Security (InfoSec) to champion a "Secure by Design" culture, directly influencing the architecture of Block's core products and infrastructure. Your mandate is to provide deep technical expertise and strategic direction to ensure that security is enabling fast, secure innovation across the business.

You Will

• Software Security Innovation: Deliver world‑class and innovative software solutions to security problems, tackling Block's top risks such as technology fragmentation and security after‑the‑fact.
• Technical Strategy & Architecture: Define the multi‑year technical strategy for software security at Block, guiding architectural decisions and ensuring alignment with engineering best practices.
• Cross‑Cutting Solution Leadership: Identify and lead the development and implementation of common, high‑leverage security solutions and infrastructure across Block's business units (Square, Cash App, TBD, etc.) to combat data sprawl and overpermissioning.
• Drive engineering excellence, specifically around security, for critical systems like tokenization platforms, ensuring integrity, performance, and scalability.
• Spearhead the security strategy and engineering excellence for mobile software and platforms across Block's product ecosystem.
• Champion security reliability engineering (SecRelEng) practices to improve the overall resilience and availability of security services and infrastructure.
• Execution Excellence: Lead technical planning and implementation for high‑priority security initiatives, acting as a technical decision maker/tie‑breaker and upholding high technical standards.
• Consultation & Guidance: Partner with engineering leaders to integrate security practices early into the development lifecycle (Secure SDLC) and provide security architecture review and threat modeling for critical systems.
• Mentorship & Enablement: Foster technical excellence within InfoSec and mentor engineers on technical execution, system design, and technology choices, driving knowledge sharing and documentation.

You Have

• Track record of exemplary technical leadership and decision‑making at a Principal or equivalent level (L8+ technical capabilities preferred).
• 10+ years of experience developing and shipping production software and critical services, with a minimum of 5 years focused on establishing and scaling security practices in a large, modern technology environment.
• Mastery of system design and architecture, with demonstrable experience solving ambiguous, domain‑heavy problems by structuring the approach, clarifying scope, and driving clarity among stakeholders.
• Deep technical understanding of security vulnerabilities, risks, countermeasures, and compensating controls, particularly in high‑volume, real‑time transaction processing environments.
• Exceptional collaboration and communication skills, with proven ability to influence executive leadership and direct engineering teams in prioritizing security roadmap items to balance security and business risks.
• Demonstrable ability to write production‑quality code/script for security automation and tooling.

Preferred

• Experience leading and driving significant technical initiatives across multiple team, organizational and product boundaries.
• Experience in the financial technology, payments, or cryptocurrency/bitcoin domain, reflecting Block's unique security characteristics.
• Experience improving engineering standards and practices for security, and building systems to achieve sub‑linear growth of security resources relative to the business (Design for Leverage, Not Coverage).

Block is an equal opportunity employer evaluating all employees and job applicants without regard to identity or any legally protected class. We will consider qualified applicants with arrest or conviction records for employment in accordance with state and local laws and "fair chance" ordinances.

We believe in being fair, and are committed to an inclusive interview experience, including providing reasonable accommodations to disabled applicants throughout the recruitment process.