Security Engineer, Anti-Abuse

Replit is the agentic software creation platform that enables anyone to build applications using natural language. With millions of users worldwide and over 500,000 business users, Replit is democratizing software development by removing traditional barriers to application creation.

The Anti-Abuse 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.

• 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 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 Big Query 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

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

• Strong programming skills in Python and/or Type Script for building detection systems and automation

• Experience with SQL and data analysis at scale (Big Query, Snowflake, or similar)

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

• Familiarity with prompt injection, jail breaking, 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.

• 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

• Languages: Python, Type Script, Go, SQL

• Data: Big Query, Hex

• Detection tools: Slurper, Netwatch, Stytch (device fingerprint);
  Clear Out (email reputation)

• CI/CD Security: Dependabot, Snyk, SAST/SCA scanners

• Infrastructure: GCP, Kubernetes

• Collaboration: Linear, Slack, Zendesk (for abuse reports)

• You prefer deep security research over building operational detection systems

• You want to focus on vulnerability management, pen testing, or bug bounty triage (that's our Security team)

• You're looking for a role with predictable, well-defined problems rather than constantly adapting to adversarial behavior

• You prefer working in isolation rather than partnering closely with Support, Legal, and cross-functional teams

• You're uncomfortable making enforcement decisions that affect real users

This is a full-time role that can be held from our Foster City, CA office. The role has an in-office requirement of Monday, Wednesday, and Friday.

• 💰 Competitive Salary & Equity

• 💹 401(k) Program

• ⚕️…