By: pjb0222

pjb0222 — Wed, 04 Feb 2009 19:46:43 +0000

And yes, there are a number of places that say to “hide” the SSID. That is a different discussion (done by people with better technical skills than mine). It only prevents the SSID from being automatically added to the available networks list and in no way prevents someone with bad intentions from finding your AP (if it is on, it is sending out a BEACON) or the SSID (there are several methods of discovering, having it in the BEACON is only one).

What “hiding” the SSID actually does. The AP will send a service BEACON anytime it is enabled. Within the BEACON the AP advertises its services (networks). In this advertisement the SSID is included in the broadcast, hence SSID broadcast. To “hide” the SSID the AP inserts a NULL SSID into the BEACON broadcast. So, your AP is still discoverable and the information that there is a configured service is there for all to see. An attacker will see the NULL SSID and know to use an alternative method to obtain the SSID. To obtain the actual SSID all the attacker must do is one of three things:
1. Wait for a system to connect/reconnect to the AP which will broadcast the SSID as part of the connection sequence.
2. Send a forged disconnect packet to a connected system so that it sends a reconnect request which broadcasts the SSID.
3. Simplest, it asks the AP what SSIDs are configured. It just sends a broadcast connect message to the AP which triggers the AP to send it a list of services which includes the SSID.

By the way, some systems have included broadcast discovery in their systems. They will discover even “hidden” SSIDs. Current OS/X anyone?

By: wlannovice

wlannovice — Mon, 02 Feb 2009 19:38:58 +0000

Thank you very much for your answer Admin89, wireless connection is enabled on the T42 in question and automatic IP as well.

Comments on: Laptop cannot detect home WLAN server

By: pjb0222

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