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I am new to WiFi and was trying to learn pentesting with the aircrack-ng suite.

In the following airodump-ng excerpt, any idea why airodump-ng is showing an access point with negative value -1 as the channel?

airodump-ng excerpt displaying a negative channel value for one line

The AP seems to be hidden but I got a reasonable PWR reading, as opposed to the ones with PWR = -1 described in Airodump-ng -1 DB networks.

Intrigued by this behaviour, I tried to use Kismet and it actually shows a positive channel for that AP.

Using Airodump-ng with option --channel and using kismet found channel I got results. Still can't figure out what is going on

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    Does this answer you? forum.aircrack-ng.org/index.php?topic=1635.0 or this? null-byte.wonderhowto.com/how-to/…
    – schroeder ♦
    Commented Jan 19, 2022 at 8:27
  • @schroeder thanks but dont think its my case I can actually see my monitoring interface hoppping betwen channels, my interface works fine, its airodump-ng that reports as channel -1 a channel that kismet using same interface find as lets say 4 or 11
    – pippo1980
    Commented Jan 19, 2022 at 8:54
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    Have you tried to reinstall airodump?
    – schroeder ♦
    Commented Jan 19, 2022 at 9:25
  • I'll give it a try
    – pippo1980
    Commented Jan 19, 2022 at 9:55
  • Answer provided by airodump's author to the OP: forum.aircrack-ng.org/index.php?topic=8776.0 "It's -1 because it just got a frame sent by a station, directed to the AP. The AP is way too far and you can't hear any frame sent by it, so we don't know what power levels it has."
    – schroeder ♦
    Commented Apr 11 at 12:22

1 Answer 1

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Airodump-ng uses "-1" to signal "I don't know".

Most frames sent by WiFi aren't tagged with what channel they're on. Airodump-ng knows what channel it was listening on when it received the frame, but there's considerable overlap between channels (if, for example, you're listening on channel 3, you can very easily receive a frame for channel 2 or channel 4).

The only frames that contain channel information are probe responses and beacons. If Airodump-ng doesn't receive one of those types of frame, all it knows is that an access point with a given MAC address or name exists.

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