Why doesn MacStumbler detect my closed network?
MacStumbler works by sending out probe requests and listening for access points to respond. Closed networks by definition don’t respond to these types of requests. Other wireless auditing programs can detect closed networks by putting the card into monitor mode and sniffing raw 802.11 frames. When legitimate clients try to associate with the closed access point, the SSID can be sniffed. Currently there is no known way to enable this type of monitor mode on Apple’s driver, so it can’t be incorporated into MacStumbler.