Staff Software Engineer, Fraud

About the role

The Fraud team is the front line defending Replit's platform from exploitation. We detect and shut down phishing deployments, prevent cryptomining on free-tier infrastructure, stop LLM token farming, and keep bad actors from weaponizing the platform against our users. This is adversarial work: attackers adapt constantly, and we build the detection systems, heuristics, and automated responses that stay ahead of them.

Responsibilities

• Design and implement LLM guardrails that detect abuse scenarios in AI-generated code and agent interactions
• Build AI-powered detection systems that use LLMs to identify malicious patterns, classify threats, and automate response decisions
• Build and operate abuse detection systems that identify phishing, cryptomining, account takeover, and financial fraud across millions of daily user actions
• Design and implement automated response mechanisms that enforce platform policies without manual intervention
• Own the full abuse response lifecycle: detection, investigation, enforcement, and handling appeals alongside Support and Legal
• Analyze attack patterns using BigQuery and Hex, turning investigation findings into new detection rules
• Maintain and extend internal detection tools (Slurper, Netwatch) that continuously monitor user activity
• Integrate and tune security scanners (SAST, SCA) in CI pipelines with tight performance SLAs
• Track abuse trends, measure detection effectiveness, and adapt defenses as attack patterns evolve

Requirements

8+ years of experience in security engineering, anti-abuse, trust & safety, or fraud detection

Strong programming skills in Python and/or TypeScript for building detection systems and automation

Experience with SQL and data analysis at scale (BigQuery, Snowflake, or similar)

Experience building or fine-tuning ML/LLM-based classifiers for security or abuse detection

Familiarity with prompt injection, jailbreaking, and other LLM-specific attack vectors

Ability to investigate complex abuse patterns and translate findings into automated defenses

Familiarity with common attack patterns: phishing infrastructure, account takeover, credential stuffing, resource abuse

Clear communication skills for working across Security, Support, Legal, and Engineering teams

Qualifications

Nice to have:

• Experience at a platform company dealing with user-generated content or compute abuse (hosting providers, cloud platforms, developer tools)
• Background in fraud detection, payment abuse, or financial crime
• Familiarity with device fingerprinting, IP reputation, and email validation services
• Experience with CI/CD security tooling (SAST, SCA, Dependabot, Snyk)
• Knowledge of container security, Linux internals, or cloud infrastructure (GCP preferred)
• Prior work with abuse reporting pipelines, trust & safety tooling, or content moderation systems

Skills

• Experience at a platform company dealing with user-generated content or compute abuse (hosting providers, cloud platforms, developer tools)
• Background in fraud detection, payment abuse, or financial crime
• Familiarity with device fingerprinting, IP reputation, and email validation services
• Experience with CI/CD security tooling (SAST, SCA, Dependabot, Snyk)
• Knowledge of container security, Linux internals, or cloud infrastructure (GCP preferred)
• Prior work with abuse reporting pipelines, trust & safety tooling, or content moderation systems

Benefits

• Competitive Salary & Equity
• 401(k) Program with a 4% match (US Only)
• Health, Dental, Vision and Life Insurance
• Short Term and Long Term Disability
• Paid Parental, Medical, Caregiver Leave
• Flexible Time Off (FTO) + Holidays
• Social Events
• Monthly Wellness Stipend
• Autonomous Work Environment
• In Office Set-Up Reimbursement (In-Office Only)
• Quarterly Team Gatherings