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Say I carry a Wi-Fi enabled phone or laptop through an area where there are WAPs. Assuming that I don't actively try to connect to them or otherwise interact with them, is it possible for the owner of that WAP to know that I was there?
I'm asking this in the context of my earlier question: Looking for MACs on the network
I was talking with a friend about my newfound ability to detect phones (and other devices with MAC addresses) on the network, and he pointed out that it might be useful to detect unknown phones on the network; I could use that data to track down anyone who was in my house and brought a Wi-Fi phone with them.
So, if I set up a logging fake WAP with no security or encryption, can I glean any useful information about the devices that come into the house? Assuming that the thief doesn't actively try to connect...
2Is it just the name of the network that's in the probe request (e.g. the string "Apple Store"), or does the request also contain something that's potentially more identifiable such as the access point's unique id? – mjs – 2014-10-25T10:57:08.647
@Spiff, Doesn't this seem to contradict Legend's post below?
– Pacerier – 2015-02-16T07:59:44.840@Pacerier [Weird, posted this comment from earlier phone and it seems like you got notified, but it looks like the comment didn't actually show up. Anyway here's the gist of it again.] No, this doesn't contradict Legend's post, it reinforces it. Actively scanning clients transmit Probe Requests that can have privacy implications. Passively scanning clients would be silent, listening for Beacons from the APs. As I said, scanning for APs is mostly active, involving transmitting Probe Requests, so you can discover that those clients are there. Maybe I'm misunderstanding your contradiction? – Spiff – 2015-02-16T21:55:30.067
2Thanks for the info. A logging fake WAP might make an interesting DD-WRT project... – Aric TenEyck – 2010-04-07T04:44:14.920
3Also, a passive scan would take more power, because the radio would need to stay on for longer. In wireless communication, counterintuitively, receiving requires more power than sending, because you won't typically know when a transmission will come. – rix0rrr – 2014-01-17T12:22:44.190
6@rix0rrr Be careful how you word that. Receiving one packet takes less power than transmitting one packet, but over the course of a Wi-Fi session (without any power save mode enabled) you may burn more total power in the receiver than the transmitter, because the receiver is basically on all the time, while the transmitter is only on when transmitting a packet. Passive scans only run the receiver 2.5x as long per channel as active scans do, but they don't run the transmitter at all. It may turn out to be a wash. – Spiff – 2014-01-18T00:02:24.000