Each time someone signs in, they complete a short camera challenge that confirms a living person is actually there — right now, in front of the device. A saved photo, a video replay, or a screen held up to the camera doesn't pass.
Because this happens on every sign-in, there is no weaker "everyday" path for an attacker to slip through.
Once signed in, an application can keep a session running without re-scanning — as with any identity system. Making the age of that proof visible to applications is on our roadmap.
Technical note
Liveness runs on AWS Rekognition Face Liveness. The confidence score is checked server-side against the organisation's threshold (90 by default, with a hard floor of 70), and the session result is fetched directly from AWS — never taken from the browser.