Service Set Identifier (SSID)

The Service Set Identifier (SSID) is the network name defined by the IEEE 802.11 standard. Access points normally advertise it in beacon frames, and clients use it to find and join a known network. Several access points can share one SSID, while each radio has its own BSSID, usually derived from its MAC address. The SSID says which network a device wants; the actual protection comes from the security mode behind it, such as WPA2 or WPA3.

Hiding the SSID from beacons is often presented as a security measure. It is readily bypassed, because the name still travels in the frames that clients exchange when they probe for and join the network, and hidden networks can make clients broadcast the name while searching for it. Filtering by MAC address fails for a similar reason, since addresses can be observed and copied. The SSID is also the bait in an evil twin attack: an attacker’s access point advertises a trusted name, and devices set to join it automatically may connect. War driving records SSIDs as it surveys.

Exam relevance: a scenario that relies on a hidden SSID or MAC filtering is likely to be checking whether the candidate sees that neither is a real control. Candidates are expected to point to strong authentication and encryption instead.