Device-linking is a cross-device sign-in or transfer flow that moves authenticated access from one device to another. Instead of typing a password on the new device, the user proves identity on a trusted device by scanning a QR code, approving a prompt, or completing a pairing step. The result is a valid session, token, or account connection on the second device.
In cyber security, device-linking matters because it can turn a legitimate authentication feature into an attack path. If an attacker socially engineers a victim into approving a pairing request, the identity platform may treat the access as normal and issue a real session. Defenders should watch for unexpected device-linking events, new device registrations, and unusual session transfers, then require strong approval controls, phishing-resistant MFA, and alerts for account changes that happen outside normal user behavior.