SSID - service set identifier
SSID is short for service set identifier.
SSID is a case sensitive, 32 alphanumeric character unique identifier attached to the header of packets sent over a wireless local-area network (WLAN) that acts as a password when a mobile device tries to connect to the basic service set (BSS) -- a component of the IEEE 802.11 WLAN architecture.
The SSID differentiates one WLAN from another, so all access points and all devices attempting to connect to a specific WLAN must use the same SSID to enable effective roaming. As part of the association process, a wireless network interface card (NIC) must have the same SSID as the access point or it will not be permitted to join the BSS.
SSID is also referred to as a network name because essentially it is a name that identifies a wireless network.
SSID is considered to be a fairly weak form of security because an SSID can be sniffed in plain text from a packet and most access points broadcast the SSID multiple times per second within the body of each beacon frame. A hacker can easily use an 802.11 analysis tool to identify the SSID. Some network administrators turn off SSID broadcasting, but a hacker can still sniff the SSID from frames that stations use when associating with an access point.
Using Multiple SSIDs
Using multiple SSIDs allows users to access different networks through a single access point. A network manager can assign different policies and functions for each SSID, increasing the flexibility and efficiency of the network infrastructure.
Learn more about SSID and minimizing WLAN security threats on Wi-Fi Planet.