The radio layer is the wireless communication layer where a device detects nearby cellular signals, measures signal quality, synchronizes with a tower, and decides whether to attach to it. In mobile networks, this is the first point of trust: before an app opens or a VPN starts, the phone must believe the signal it is hearing is part of a legitimate network.
This matters because attackers can target the radio layer with rogue base stations or other signal-deception techniques. By imitating normal network behavior, a fake tower may trick devices into revealing identifiers, connecting under weaker conditions, or following an attacker-controlled path. Defenses focus on strong network authentication, careful device and operator configuration, anomaly detection, and standards that reduce the value of unauthenticated signals. In practice, radio-layer security is about trusting the air only after it has been verified.