Page 790 - (ISC)² CISSP Certified Information Systems Security Professional Official Study Guide

If multiple base stations or wireless access points are involved in the
same wireless network, an extended station set identifier (ESSID) is

defined. The SSID is similar to the name of a workgroup. If a wireless
client knows the SSID, they can configure their wireless NIC to
communicate with the associated WAP. Knowledge of the SSID does
not always grant entry, though, because the WAP can use numerous
security features to block unwanted access. SSIDs are defined by
default by vendors, and since these default SSIDs are well known,
standard security practice dictates that the SSID should be changed to

something unique before deployment.

The SSID is broadcast by the WAP via a special transmission called a
beacon frame. This allows any wireless NIC within range to see the
wireless network and make connecting as simple as possible. However,
this default broadcasting of the SSID should be disabled to keep the
wireless network secret. Even so, attackers can still discover the SSID
with a wireless sniffer since the SSID must still be used in

transmissions between wireless clients and the WAP. Thus, disabling
SSID broadcasting is not a true mechanism of security. Instead, use
WPA2 as a reliable authentication and encryption solution rather than
trying to hide the existence of the wireless network.

Disable SSID Broadcast

Wireless networks traditionally announce their SSID on a regular
basis within a special packet known as the beacon frame. When the
SSID is broadcast, any device with an automatic detect and
connect feature not only is able to see the network but can also
initiate a connection with the network. Network administrators
may choose to disable SSID broadcast to hide their network from

unauthorized personnel. However, the SSID is still needed to direct
packets to and from the base station, so it is still a discoverable
value to anyone with a wireless packet sniffer. Thus, the SSID
should be disabled if the network is not for public use, but realize
that hiding the SSID is not true security because any hacker with
basic wireless knowledge can easily discover the SSID.