Senior Security Engineer (Blockchain Security)

As a Senior Security Engineer on Nubank's Blockchain Security team, you own the security posture of Nu's crypto operation. You sit within the Product Security & Assurance BA, part of the Information Technology and Security (ITSec) BU, supporting the security of Nu's crypto products as the company expands globally. Your work directly protects customer funds and Nu's ability to run crypto products at scale while meeting regulatory requirements.

What you'll do

• Apply an offensive security mindset to crypto and blockchain products by simulating attacks, running penetration tests and security assessments, and turning findings into concrete mitigations.
• Drive product security across the crypto portfolio through threat modeling, security-by-design reviews, and embedding secure practices into the development lifecycle.
• Build, operate, and improve in-house security services and tooling that integrate directly with crypto products, such as hardened ingress and edge controls, security monitoring and anomaly alerting, secure secret-management, and automated security-review tooling.
• Ensure the crypto operation meets regulatory requirements by mapping controls to applicable regulations, supporting audits, and producing evidence that regulators and internal risk teams expect.
• Collaborate with product and engineering teams to design secure blockchain architecture and embed security-by-design into new products.
• Contribute to security policies, standards, and guidelines that govern blockchain security operations.
• Use AI to raise the leverage and quality of security work by building and running AI-assisted tooling for threat modeling, code and vulnerability review, and attack simulation.
• Stay current on emerging attack vectors, exploits, and best practices across product and blockchain security, and share that knowledge across the team.

What you bring

• Strong product security and/or offensive security background, including penetration testing, vulnerability assessment, attack simulation, and incident response.
• Experience embedding security into product development through threat modeling, secure SDLC, and security-by-design reviews.
• Hands-on software engineering ability to build and operate security services and automation. You can write production code in Clojure or another modern language with willingness to learn Clojure.
• Solid working knowledge of blockchain and cryptocurrency fundamentals, including how blockchains, wallets, keys, and smart contracts work and their security implications.
• 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 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, with strong analytical and problem-solving skills, and clear written and spoken English for technical and non-technical audiences.

Nice to have

• Deeper knowledge of blockchain and crypto internals, including consensus algorithms, cryptographic protocols, and smart contracts.
• Experience auditing smart contracts such as Solidity or working with DeFi protocols.
• Experience integrating with third-party crypto custody and infrastructure providers such as Fireblocks or Circle.
• 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.

What we offer

• Chance to earn equity at Nubank
• Food and meal card (Vale-Refeição and/or Vale Alimentação)
• Public transportation commuting benefit (Vale-Transporte)
• NuCare, a psychological, financial, and legal assistance program
• Life insurance
• Medical plan
• Dental plan
• NuLanguage, a language course program
• Nucleo, a learning platform with courses
• Extended parental leave
• Daycare allowance
• Parental consultancy
• Work-from-home allowance
• Gym partnerships
• 30 days of paid vacation
• Relocation assistance package, if applicable

Location: São Paulo, Campinas, Rio de Janeiro, or Belo Horizonte, Brazil.

Work model: Hybrid, with office presence at least twice a week on strategic days designed to maximize team connection and collaboration.

About Nubank

Nubank serves more than 140 million customers with a mission to fight complexity and empower people. The company leads an industry transformation through innovative products and human-centered services, powered by proprietary technology and data at scale to promote financial access, advancement, and transparency.