A broadcast medium is a communication channel where one transmission can be received by many listeners at once. Radio, Wi-Fi beacons, and maritime systems such as AIS all use this pattern: a sender emits data, and any receiver in range can capture it. In security terms, that means the channel is efficient for distribution, but it also exposes the message to eavesdropping, replay, spoofing, and jamming.
Broadcast media matter because software cannot assume the source is private or exclusive. Defenders treat incoming broadcasts as untrusted input and validate format, timing, and plausibility before using the data. They often correlate broadcasts with other sensors or authenticated channels to detect false or injected messages. In attacks, adversaries may exploit the one-to-many nature of the medium to mislead many systems at once, while in defenses it enables wide-area alerts and shared situational awareness.