Machine Learning Engineer

ppbJoin Proton and build a better internet where privacy is the default /b /p pProton was founded in 2014 by scientists from CERN on a simple truth: bprivacy is a fundamental human right /b. Since then, we’ve built the world’s largest encrypted email service (Proton Mail) and expanded into Proton VPN, Proton Drive, Proton Pass, and Proton Calendar—tools used by millions globally to protect their freedom, fight censorship, and keep their data safe. In some situations, Proton has literally helped save lives! We are profitable, independent (no VC control), and selectively hire from the top 1% of applicants. Our 500+ team members across 50+ countries come from leading organizations and elite academic backgrounds. We move fast, keep hierarchy light, and prioritize impact over optics. If you want to do meaningful work with exceptionally high‑caliber people, this is it. Join us and do work you can truly be proud of. Check our open‑source projects here! /p h3About the role /h3 pThe MSA team (Mail Delivery, Spam, and Anti‑Abuse) is a multidisciplinary group founded in 2019 to solve complex security challenges across the Proton ecosystem. We build sophisticated systems from scratch that combine human intelligence and machine learning to make tens of millions of real‑time or asynchronous decisions daily. Our focus areas include: /p ul liMail delivery and spam prevention /li liAbuse detection /li liAccount security /li liSite reliability and resilience /li /ul pOver the past few years, our custom systems have: /p ul liReduced spam filter misclassifications by over 70% /li liBlocked millions of abusive bulk signups /li liProtected hundreds of thousands of users from account compromises /li liMitigated hundreds of DDoS attacks /li /ul pRecently, we’ve expanded our impact with bProton Sentinel /b (an AI‑human hybrid security program) and bProton CAPTCHA /b (our own puzzle system to detect and prevent abuse). We’re now scaling our capabilities with agentic AI to enable autonomous threat detection and response. /p pIn 5 years, we’ve grown from 2 engineers to 40+ engineers and analysts across 3 continents, operating 24/7. We’re looking for curious, collaborative, and impact‑driven engineers who thrive in a startup environment and want to shape the future of secure AI. /p h3What You Will Do /h3 ul liDesign and deploy scalable ML systems using modern MLOps practices, including real‑time inference, model monitoring, and automated retraining pipelines. /li liArchitect agentic AI systems capable of autonomous threat detection, adaptive policy enforcement, and self‑healing security responses. /li liBuild tools for model development, debugging, and explainability to accelerate iteration and transparency. /li liOptimize ML workflows for distributed environments to handle large‑scale data processing. /li liCollaborate cross‑functionally with security analysts, backend/frontend engineers, and customer support to align technical solutions with user needs. /li liAdvance the state of ML for anti‑abuse and account security, exploring cutting‑edge techniques like adversarial robustness, graph‑based anomaly detection, and privacy‑preserving AI. /li /ul h3What You Bring /h3 ul liDegree in Computer Science or a related quantitative field, with 2+ years hands‑on experience in building and running ML systems. /li liProduction‑level ML expertise: You’ve shipped models that handle real‑world scale and complexity. /li liHands‑on experience with LLMs in agentic environments. /li liStrong software engineering skills: Proficiency in Python, with a solid understanding of backend and server fundamentals. /li liStatistical rigor: Deep understanding of probability, hypothesis testing, and experimental design. /li /ul h3Bonus Points For /h3 ul liExperience with adversarial ML or red‑team ML systems. /li liExperience working on distributed systems. /li liContributions to open‑source security/privacy tools. /li liKnowledge of federated learning, differential privacy, or on‑device inference. /li liFamiliarity with graph‑based anomaly detection or knowledge graphs. /li liTechnical leadership: Experience owning projects, mentoring peers, and driving technical direction. /li liSecurity mindset: Familiarity with abuse patterns, adversarial attacks, or threat intelligence. /li /ul h3Why Join Us? /h3 ul liImpact at scale: Your work will protect millions of users globally. /li liCutting‑edge tech: Tackle challenges like agentic AI, real‑time threat detection, and privacy‑preserving ML. /li liCollaborative culture: Work with a global team of experts in security, ML, and systems engineering. /li liGrowth opportunities: Lead initiatives, mentor others, and learn across a diverse technology stack. /li liMission‑driven: Contribute to a privacy‑first internet where users control their data. /li /ul h3What We Offer /h3 ul liWork that matters: millions of people trust Proton with their privacy. We answer only to our users — not advertisers, not investors with conflicting agendas, not governments. /li liA great team: Our team is diverse, collaborative, and tight‑knit. /li liTechnology: you’ll get the right hardware and the right software you need to do your best work. /li liLearning development: we invest in your growth because sharp people make us better. /li liEmployee benefits: strong health coverage, solid retirement options, generous leave, and wellness support. /li liStock options: at Proton, we all have the opportunity to be owners of the company. /li liIn‑person collaboration: Amazing things happen when passionate, smart, and purposeful people get together. /li liFood: lunch and snacks are on us every day in our offices. /li liTransport: we cover public transport, bike allowances, or parking. /li liFlexible working: you own your schedule. /li /ul h3Our Commitment to Diversity and Inclusion /h3 pAt Proton, we believe diversity drives innovation and strengthens our mission to provide privacy as a default for all. We are committed to fostering an inclusive environment where all individuals, regardless of race, ethnicity, gender, age, sexual orientation, physical ability, or socio‑economic background, feel valued and empowered. We strive to create equal opportunities, promote open dialogue, and support continuous learning to ensure every voice is heard and respected. If you need any extra support or reasonable adjustments during the hiring process, please let your talent partner know. /p h3Candidate Privacy Notice /h3 pWhen you apply for a position, refer a candidate, or are considered for a role at Proton Technologies AG (Proton, we, us, or our), your information is stored in Greenhouse, in accordance with their Service Privacy Policy. This information is used to evaluate your suitability for the posted position. We also retain this information for consideration for future roles that you may apply for or that we believe may align with your background and skills. If we no longer have a legitimate business need to process your information, we will either delete or anonymize it. Should you have any inquiries about how we use or manage your information, or if you wish to access, correct, or delete your data, please contact our privacy team at Proton does not accept unsolicited resumes from any sources other than directly from candidates. /p /p #J-18808-Ljbffr