Senior Security Engineer (Blockchain Security)

About Nu Nu serves more than 140 million customers, guided by a mission to fight complexity and empower people. The company has been leading an industry transformation through innovative products and human-centered services.   Proprietary technology and data at scale power Nu’s digital platform, built to promote financial access, advancement, and transparency. Its business model thrives on customer love and lower costs, feeding a flywheel of growth and profitability. Visit our Institutional Page About the role The Blockchain Security team sits within the Product Security & Assurance BA, part of the Information Technology and Security (ITSec) BU. Our mission is to support the security of Nu's crypto operation. In the context of Nu's global expansion, keeping these products secure, and demonstrably compliant with financial regulators, is a direct condition for our ability to operate and grow. As a Senior Security Engineer on this team, you own the security posture of our crypto operation. You are the person who thinks like an attacker so our products can withstand real ones: finding vulnerabilities before adversaries do, embedding product security into how crypto products are designed and built, and making sure our controls satisfy both internal risk standards and external regulatory requirements. You won't just run security tools. You'll build and operate the ones that protect our crypto products, from hardened ingress and monitoring/alerting systems to secure secret-management and automated security-review tooling. Your work directly protects customer funds and Nu's ability to run crypto products at scale.   You'll be responsible for Applying an offensive security mindset to our crypto and blockchain products: simulating attacks, running penetration tests and security assessments, and turning findings into concrete mitigations. Driving product security across the crypto portfolio: threat modeling, security-by-design reviews, and embedding secure practices into the development lifecycle. Building, operating, and improving in-house security services and tooling that integrate directly with our crypto products, for example hardened ingress/edge controls, security monitoring and anomaly alerting, secure secret-management, and automated security-review tooling. Ensuring our crypto operation meets regulatory requirements: mapping controls to applicable regulations, supporting audits, and producing the evidence regulators and internal risk teams expect. Collaborating with product and engineering teams to design secure blockchain architecture and embed security-by-design into new products. Contributing to security policies, standards, and guidelines that govern blockchain security operations. Using AI to raise the leverage and quality of security work: building and running AI-assisted tooling for tasks like threat modeling, code and vulnerability review, and attack simulation, and helping the team push the frontier of what AI-first security engineering looks like. Staying current on emerging attack vectors, exploits, and best practices across product and blockchain security, and sharing that knowledge across the team. We are looking for a person who has Must have Strong product security and/or offensive security background (penetration testing, vulnerability assessment, attack simulation, incident response). Experience embedding security into product development: threat modeling, secure SDLC, security-by-design reviews. Hands-on software engineering ability: you can build and operate security services and automation, not just use off-the-shelf tools. Comfortable writing production code (we work heavily in Clojure; strong experience in any modern language plus willingness to learn Clojure is fine). Solid working knowledge of blockchain and cryptocurrency fundamentals, including how blockchains, wallets, keys, and smart contracts work, enough to reason about their security (expert-level depth not