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Comment by bfirsh | Hacker News Reader

This reminded me of this explanation of how MacBooks (and presumably other devices) manage to reconnect to Wifi so quickly after waking from sleep: http://cafbit.com/entry/rapid_dhcp_or_how_do

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And in the process walking all over various security best practices?

And was there not a similar security snafu involving iPhones broadcasting past ssids every time they tried to connect to a access point?

Don't most (mobile) devices broadcast all known SSIDs just in case a network is available and hidden? I don't really know a lot about the subject matter, but as I recall this does not apply to just iPhones.

I also remember an installation at the Datenspuren in Dresden with a monitor showing all of these SSIDs it intercepted with people walking past and being astounded how the device knew their home network name^^

Almost all Android devices do the same, they just send probe requests with all known networks. That is why you can automatically connect to "hidden" networks. Just run kismet or wireshark and see for yourself.

And it can be used to uniquely identify devices and track them with fairly standard hardware

Doesn't a MAC address get broadcast anyway? Unless wifi devices are randomizing their MAC addresses that seems like a fairly trackable thing.

IIRC newer iOS devices do randomize the MAC address used for probes.

Well, this traffic is sent after link establishment, so at least in a WPA network, it's already encrypted (hopefully it doesn't do the same in unencrypted networks). Still, any member of the network could sniff the MACs of the last few APs the device was connected to, which as you said, it's a security/privacy leak.

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