The Illusion of Hidden SSIDs
First a few definitions:
BSS (Basic Service Set) – The basic building block for a WLAN, a single access point and its clients SSID (Service Set IDentification) – String used as the network name for WLANs
BSSID (Basic Service Set IDentification) – The unique identifier for a BSS
ESSID (Extended Service Set IDentification) – Two or more BSS that share the same SSID
Quite often, we are asked to make a recommendation on whether to hide or not to hide SSIDs. In this case, security through obscurity is a myth. “Hiding” an SSID usually consists of turning off the beaconing mechanism of an access point. This can be effective in obscuring the SSID for the casual passer-by, but does nothing to really hide the network. Someone of any skill level using a wide variety of free tools can discover the network. Even Windows 7 natively identifies the network as hidden. This discovery is possible because there are other mechanisms at work which broadcast the SSID. “Hiding” an SSID by turning off beacons is one mechanism. Probe requests from client devices also contain this data, as well as probe responses, association requests, etc. Hiding beacons can also impede roaming and introduce technical and operational issues when trying to troubleshoot user connectivity.
The approach that you want to take is looking at your organization’s needs. What are the use-cases? What SSIDs do you need? What authentication and encryption methods are supported? Can you consolidate by using role-based access? Once you have an assessment of your needs, you can put a plan together taking into consideration the appropriate security mechanisms.