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.

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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 required, but real familiarity is).

• Strong knowledge of recent and past attack vectors and exploits, and how to remediate them.

• Experience with security frameworks such as OWASP and the NIST Cybersecurity Framework (CSF).

• Fluency with AI-assisted engineering: using coding agents and LLMs in daily work, with good judgment about where they help, where they don't, and how to review their output critically.

• Familiarity with AWS, and solid grounding in operating systems, networks, databases, and infrastructure architecture.

• Ability to work autonomously and proactively, strong analytical/problem-solving skills, and clear written and spoken English for technical and non-technical audiences.

Nice to have

• Deeper knowledge of blockchain/crypto internals: consensus algorithms, cryptographic protocols, smart contracts.

• Experience auditing smart contracts (e.g. Solidity) or working with DeFi protocols.

• Experience integrating with third-party crypto custody/infrastructure providers (e.g. Fireblocks, Circle, and similar).

• Exposure to regulatory or compliance requirements in a financial or crypto context.

• Experience with bug bounties and/or CTFs.

• Certifications such as OSCP, OSWE, or Certified Blockchain Security Professional.

Location for this opportunity

• São Paulo, Brazil

• Campinas, Brazil

• Rio de Janeiro, Brazil

• Belo Horizonte, Brazil

Our Benefits

• Chance of earning equity at Nubank

• Food/ Meal Card (Vale-Refeição and/or Vale Alimentação)

• Public Transportation Commuting Benefit (Vale-Transporte)

• NuCare - Psychological, Financial and Legal Assistance Program

• Life Insurance

• Medical Plan

• Dental Plan

• NuLanguage - Language Course Program

• Nucleo - Our learning platform of courses

• Extended Parental Leave

• Daycare Allowance

• Parental Consultancy

• Work-from-home Allowance

• Gym Partnerships

• 30 days of paid vacation

• Relocation Assistance Package, if applicable

Work Model for this Role Our hybrid work model brings us to the office at least twice a week, on strategic days designed to maximize team connection and collaboration. For more details, visit https://building.nubank.com/nu-hybrid-work-model/

Our recruitment process may involve the use of artificial intelligence-enabled tools, such as automated interview transcription and analysis, to support the evaluation process. Artificial intelligence is not used to make final hiring decisions; all decisions are made by human reviewers.

To maintain a consistent and fair process for every candidate, Nu does not provide individualized technical feedback. See how our policy works here