Staff Applied Machine Learning Engineer - Fraud & Abuse
Block, Inc. is a technology company building tools for economic empowerment, operating a portfolio of financial brands including Square, Cash App, Afterpay, TIDAL, Bitkey, and Proto. It serves sellers, consumers, artists, and bitcoin users through payments, banking, buy-now-pay-later, music streaming, and bitcoin self-custody and mining products.
About Block, Inc.
Block, Inc. builds technology aimed at increasing access to the global economy. Its brands each unlock different aspects of the economy: Square makes commerce and financial services accessible to sellers; Cash App is an easy way to spend, send, and store money; Afterpay (Clearpay in the UK) helps customers manage spending over time; TIDAL is a music platform empowering artists as entrepreneurs; Bitkey is a self-custody bitcoin wallet; and Proto builds open, accessible bitcoin mining hardware and services. Block has been a long-time advocate for bitcoin, integrating bitcoin buying/selling and Lightning Network payments into Cash App and Square, funding open-source bitcoin infrastructure through Spiral (including the Lightning Development Kit), and engaging in bitcoin policy advocacy through groups like COPA, the Digital Energy Council, the Crypto Council for Innovation, and the Texas Blockchain Council. The company also runs a significant open source program (contributing to projects like Goose, an on-machine AI developer agent, OkHttp, Retrofit, gRPC, Envoy, and MySQL) and an AI research effort, including co-founding the Agentic AI Foundation with Anthropic and OpenAI. Block serves individual consumers, small and medium-sized businesses/merchants, artists, and developers.
Skills
About the Role
You will design, build, and operate production machine learning decisioning systems that detect and prevent fraud and abuse across payments, accounts and marketplaces. You will work with ML modelers, risk analysts, product, compliance and operations to respond quickly to evolving abuse patterns while preserving access for legitimate customers. You will own the end to end lifecycle from data contracts to model deployment and monitoring, and you will help improve feedback loops and AI assisted workflows for triage, investigation and incident learning.
Requirements
- 12+ years building and operating production software and ML systems for business critical products.
- Deep expertise in fraud/risk domains such as payment fraud, identity/account integrity, merchant or marketplace risk, scams, trust and safety, abuse prevention, or compliance decisioning.
- Strong production ML judgment across feature pipelines, model serving, evaluation, monitoring, low latency integration, safe rollout, and incident response.
- Sound judgment around false positive tradeoffs, noisy labels, adversarial behavior, customer harm, and cross functional decisions.
- Experience using AI assisted engineering tools with appropriate verification, testing, and review for high stakes systems.
- Experience with graph based fraud detection, behavioral sequence models, embeddings, entity resolution, anomaly detection, or human in the loop review.
- Experience building fraud operations tooling for triage, case management, alert clustering, graph exploration, or policy simulation.
- Experience with regulated financial services, model governance, auditability, explainability, or decision logging.
Responsibilities
- Build and operate real-time and batch ML decisioning systems for payment fraud, scams, identity and account integrity, merchant and marketplace risk, and abuse prevention.
- Integrate behavioral, graph, device, network, event-stream, and third-party signals into low-latency model serving, decision APIs, and product controls.
- Own the production lifecycle for risk decisions including data contracts, feature quality, online offline consistency, monitoring, drift detection, safe rollout, rollback, and incident response.
- Develop feedback loops and verified AI assisted workflows for triage, investigation support, alert clustering, graph exploration, simulation, and post incident learning.
- Partner with modelers, analysts, product, compliance, and operations to balance fraud losses, customer access, false positives, product velocity, support burden, and long term trust.
- Create reusable decision and evaluation capabilities that product services, internal tools, and AI assisted workflows can safely consume.
Benefits
- Remote work
- Medical insurance
- Flexible time off
- Retirement savings plans
- Modern family planning
