> If the network name of a wireless network (SSID) is not broadcast, the clients must search for it with probe requests. So if you have one AP and 100 wireless devices, you partially limit exposure of the network name with one device while causing 100 devices to expose it instead.
Especially, mobile devices like laptops, smartphones etc will then have to send probe requests constantly, even if youre away from home... informing any eavesdropper around of essid and probably also bssid.
Most OSes do this anyway to speed up the connection process (try to attach to last n networks and see what sticks). Can be abused to learn about past locations of that device by asking one of the wifi location api databases (iOS, win, google/android):
tl;dr from the article:
> If the network name of a wireless network (SSID) is not broadcast, the clients must search for it with probe requests. So if you have one AP and 100 wireless devices, you partially limit exposure of the network name with one device while causing 100 devices to expose it instead.