What is a SSID?

The SSID (Service Set IDentifier) is a token which identifies an 802.11 (Wi-Fi) network.

The SSID is a secret key which is set by the network administrator.

You must know the SSID to join an 802.11 network. However, the SSID can be discovered by network sniffing. By default, the SSID is part of the packet header for every packet sent over the WLAN.

SSID Security Issues

The fact that the SSID is a secret key instead of a public key creates a key management problem for the network administrator. Every user of the network must configure the SSID into their system. If the network administrator seeks to lock a user out of the network, the administrator must change the SSID of the network, which will require reconfiguration of the SSID on every network node. Some 802.11 NICs allow you to configure several SSIDs at one time.

Default SSID's

Most 802.11 access point vendors allow the use of an SSID of "any" to enable an 802.11 NIC to connect to any 802.11 network. This is known to work with wireless equipment from Buffalo Technologies, Cisco, D-Link, Enterasys, Intermec, Lucent, and Proxim. Other default SSID's include "tsunami", "101", "RoamAbout Default Network Name", "Default SSID", and "Compaq".

Disabling SSID Broadcasting

Many Wireless Access Point (WAP) vendors have added a configuration option which lets you disable broadcasting of the SSID. This adds little security because it is only able to prevent the SSID from being broadcast with Probe Request and Beacon frames. The SSID must be broadcast with Probe Response frames. In addition, the wireless access cards will broadcast the SSID in their Association and Reassociation frames. Because of this, the SSID cannot be considered a valid security tool.