Under setup -> AP radio -> hardware you can see a "Allow "broadcast" SSID to associate" yes/no radio button. Selecting no will disable broadcast SSID
Turning off broadcast-SSID removes the SSID from the beacons (which are sent every 100ms by default), but the SSID is still visible in all probe-request/response frames (much less frequent, but **easily** sniffed by anyone with the intent to hack a WLAN).
My take is also that disabling broadcast-SSID is **not** a security precaution. SSID is the **NAME** of the WLAN. However, most WLAN security articles in the press mention turning broadcast-SSID off as part of a security policy (without really justifying how it makes the network any more secure).
If you are looking to make your wireless LAN more secure, you should look into LEAP, VPN or many of the other security solutions available.
