Impossible travel: What it is, how it works, and how to defend against it

Impossible travel detection leverages the physical impossibility of a person being in two places at once to identify potential security breaches such as credential theft and session hijacking. This method involves analyzing login events from different locations and times; if the travel speed between them exceeds what's physically feasible, the event is flagged as suspicious. Despite its simplicity, naive implementations often result in false positives due to factors like VPNs, mobile network routing, and GeoIP inaccuracies. To reduce noise, mature systems incorporate device fingerprinting, IP classification, user behavior baselines, and session context to filter out benign anomalies. WorkOS Radar, a security layer integrated with AuthKit, exemplifies this approach by using device fingerprinting and geolocation tracking to maintain a low false positive rate, offering configurable response actions such as blocking, challenging, or notifying users of suspicious activity. Radar is part of a broader defense strategy that includes bot detection and credential stuffing defenses, allowing users to customize rules for specific scenarios and manage alerts through a real-time dashboard.