Castle blog · May 2026
Released an open-source disposable phone number list and described it as a fraud-intelligence resource for fake signups, multi-accounting, referral abuse, and SMS verification abuse.
Company research
Public company, workplace, funding, and market signals
Updated Jul 30, 2026
Overview
Castle (castle.io) is a Brooklyn-based, privately held developer platform for bot detection, fraud prevention, and account security. It sells APIs and SDKs that combine behavioral analysis, device fingerprinting, and risk scoring to stop fake signups, account takeovers, multi-accounting, transaction abuse, and similar threats in real time.
Primary product
Developer-grade fraud prevention and bot detection APIs/SDKs
Founded
2015
Headquarters
Brooklyn, New York, United States
Team size
11-50
Industry
Software Development
Sub-industry
Fraud prevention and account security software
Offices
Brooklyn, New York, United States (HQ)
Open Positions
2 jobs at Castle
Backend Software Engineer
RemoteEngineering & ProductHarvard Square1y ago
Remote