Castle enables online businesses of all sizes to detect and prevent user account fraud, a technology previously only available to banks and large financial institutions. Whether you’re building a bitcoin service, e-commerce store, mobile app, or any other customer-facing application, Castle's API's lets you add account hijack protection.  Intelligent protection against user account fraud and hijacks. Castle learns from users' behavior, and identifies suspicious activity in real-time. Castle tracks fraudsters based on device fingerprint, keystrokes, site browsing history, and hundreds of other signals. Administrators are alerted and high-risk accounts are automatically locked the second someone starts behaving suspiciously or tries to log in with a stolen password.