SSID is the acronym for Service Set Identifier, a 32-character identifier for Wireless local Area Networks (WLANs) which a user may want to latch onto. It is also referred to as the network name. All the wireless devices on a particular network need to have the same SSID in order for them to “communicate”. The SSID differentiates one WLAN from another and a device cannot access a particular WLAN unless it provides a similar SSID. The WLANs identified by this method use 802.11 (or WI-FI) standards that were developed by IEE LAN/MANS Standards committee. The SSID on wireless devices can be set manually configuring the SSID on the network settings, or it can be done automatically by not specifying any particular SSID. If someone configures the same SSID with other Wireless Application Points (WAPs), this may lead to conflict with those networks.

Many a network administrators has set the SSID on an access point that distributes the SSID to the wireless devices near it. This obviously comes with a security concern that unauthorized users may access some private data in one of the devices. SSID can be “sniffed out” from a packet of data and this may enable unauthorized access. Some new devices however, have tried to deal with that concern by having the ability to disable the automatic SSID broadcast to other devices and thus to minimize security concerns.

There is a widely held belief that one can improve their network security simply by disabling the SSID broadcast to other devices. The fallacy of this tactic is that every time the user tries to connect to the network (by entering the correct SSID), the SSID itself is transmitted in plain text, which makes it easy for an eavesdropper, using a WLAN network detector software like Kismet, to use the now revealed SSID to access the network without even trying too hard (Kismet works passively, and waits for a nearby device to connect, and later “pounces” on the SSID).

There are identifiers that are often confused with SSID, though many people use the term “SSID” to define them in the loose sense. One is called Extended Service Set Identification (ESSID) while the other is called Basic Service Set Identification (BSSID). BSSID is a temporary network used with no access point whereas ESSID may use an access point.

There are at least two wireless networks protection systems; one is called Wired Equivalent Policy, or WEP, while the second one is called Wi-Fi Protected Access (WPA). WPA is the more widely accepted of the two, in part because it was designed to escape some of the shortcomings that were evident in WEP, which is the earlier of the two systems. Thus, the most effective way to protect the wireless connection is to use these systems and at the same time keep the SSID broadcast function on, because that makes it much more difficult for an unauthorized person/eavesdropper to gain access to the network using Kismet and other eavesdropping software.

For more information read What is SSID

http://www.tech-faq.com/ssid.shtml