SSIDs are useless
The 802.11 standard specifies the SSID (service set identifier) as a form of password for a user's radio
NIC to join a particular wireless LAN. 802.11 requires that the user's radio NIC have the same SSID as
the access point have to enable association and communications with other devices. In fact, the SSID
is the only "security" mechanism that the access point requires to enable association in the absence
of activating optional security features.
The use of SSIDs is a fairly weak form of security, however, because 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. In addition, Windows XP does a great job of "sniffing" the
SSID in use by the network and automatically configuring the radio NIC within the end user device.
Some network administrators turn off SSID broadcasting (which deletes the SSID from the beacon
frames), but a hacker can still sniff the SSID from frames that stations use when associating with an
access point. They just have to wait until someone associates or re-assoicates (e.g., when roaming)
with the network.
Aside from sniffing the SSID, many wireless LAN administrators make it even easier by using the
vendor's default SSIDs, which are pretty well known. For example Cisco uses tsunami and most other
vendors use the name of their company as the default SSID.
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