38

Okay, so I have lost my tablet somewhere in my flat and have been searching for hours already. It is an Android device, which seems to have wifi enabled (responds to pings), but doesn't seem to react to cloud-based messages. Furthermore, I have Cerberus installed on it, but cannot connect to it.

Is there a way of physically finding the device by measuring the signal strength from different locations in my flat?

I know it is theoretically also possible to triangulate a wifi signal, and even though I have four Linux based wifi receivers I do not know any non-commercial software that is capable of doing so.

samthebrand
  • 340
  • 1
  • 4
  • 22
Force
  • 652
  • 1
  • 8
  • 16
  • 4
    I know you can get the signal reception using `airodump-ng` (part of the `aircrack-ng` tool suite) if you have a compatible Wifi card and a Linux distro up and running. You'll see something [like this](http://www.aircrack-ng.org/doku.php?id=airodump-ng) with the signal reception listed as `PWR` (in decibels). If you keep pinging the device throughout this, you should see the `airodump-ng` screen update much quicker with the MAC address of the device. You should then be able to move around with your laptop, trying to increase the `PWR` until you find the device. – Breakthrough May 28 '13 at 20:16
  • Also see (not a dupe) [Wifi direction/location finding](http://superuser.com/questions/63966/wifi-direction-location-finding). – Karan May 28 '13 at 20:18
  • There's no way to triangulate unless you have directional antennae. Some WiFi boxes have two antennae, and they will probably (but not certainly) produce the strongest signal at right angles to the line between the antennae. If you could somehow read signal strength while rotating such a WiFi box you might be able to get a rough directional reading. – Daniel R Hicks May 28 '13 at 20:37
  • @Breakthrough Thanks for the airodump advice - I can see the device, however it stays at -127 PWR (unlike my phone). I take a wild guess that this is the power output **to the station** and not to the monitoring wifi card? – Force May 28 '13 at 20:37
  • @Force that's an invalid power value (0xFF casted as a signed char). Have a look through some Google results for how to fix that (it *might* be the drivers or monitor interface you're using). – Breakthrough May 28 '13 at 20:40
  • Another way to have a directional antenna is to have it point horizontally. In this case the strongest signal would probably be the direction the antenna points (or 180 degrees from that), though again this is a guess, since an antenna's internal construction affects this. – Daniel R Hicks May 28 '13 at 20:40
  • 21
    (Of course, the other option is to clean up your flat. You know you've been meaning to do that for about 2 years now.) – Daniel R Hicks May 28 '13 at 20:42
  • @Breakthrough well I doubt it is related to the monitor device, as PWR values for other devices *are* changing... also it shows a rate of 0e - 0e for the tablet... – Force May 28 '13 at 20:47
  • @Force hmm, never mind then. Does the value change when moving closer/further away from the AP? – Breakthrough May 28 '13 at 20:52
  • @Breakthrough no, not at all – Force May 28 '13 at 20:54
  • @Force out of curiosity, does your AP display the device's signal power? – Breakthrough May 28 '13 at 20:56
  • Only as bars (2/4 are green) – Force May 28 '13 at 20:59
  • Have you found it yet? If your question really is "How do I find my lost device?" rather than "How do I find it using specific technique X", you may want to check out Plan B from Lookout. You can find it on the Google Apps store & it will let you remotely download & activate an alarm to help you find it (assuming it still has battery ...) – yosh m May 28 '13 at 21:43
  • 1
    Like I said, it seems that it doesn't respond to CMS messages, as Cerberus cannot connect. Also Plan B does only work for gingerbread devices – Force May 29 '13 at 07:32
  • 2
    Not a direct answer to your question, but [Plan B](https://play.google.com/store/apps/details?id=com.lookout.labs.planb) is specifically for situations where you've lost track of your Android device and didn't have any sort of "finder" app on it. – ale May 29 '13 at 13:03
  • 3
    Plan B is mentioned before, but doesn't work on Android 3.1+ anymore (as they disallowed apps to register BroadcastReceivers before being manually opened by the user), otherwise I would have written my own app for that... – Force May 29 '13 at 16:44
  • 3
    Mandatory Bash reference: http://bash.org/?5273 – abstrask May 31 '13 at 16:14
  • 1
    Can you push [this app](https://play.google.com/store/apps/details?id=com.androidlost) thru Google Play? – harrymc Aug 09 '13 at 06:33
  • @AlEverett I wonder if he's triangulated the location yet? It's been nearly three months since he lost it. – Ellie Kesselman Aug 15 '13 at 03:33
  • 2
    @FeralOink: The bounty is from a different person than the poster, but equally unresponsive. – harrymc Aug 15 '13 at 08:11

5 Answers5

13

Something that may work:

Go to the hardware store and buy some brass mesh and build a cone. You'll probably need to layer the mesh, then hold your phone in the middle of the cone. The brass mesh should block all radio signals, so if you get a signal, its coming from the direction of the open area of the cone. In theory, you can use this to home in on the device.

FYI, the brass mesh is one component in building a SCIF.

Keltari
  • 71,875
  • 26
  • 179
  • 229
9

You can always use a Network Monitoring Software Tool like MoocherHunter to triagulate the geolocation of your wifi enabled device.

Actually the mentioned tool is used to triangulate the wifi moochers, but can do the trick for you,given that,the android device is conected to your LAN.

Your router's administrative console can help you find out more about your wireless network activity.It should provide a list of IP addresses, MAC addresses, and device names that it is connected to.with the help of these details this tool will help you locate the device down within 2 meters.(as per developers)

MoocherHunter has been used for law enforcement organizations in Asia to track Wi-Fi moochers.

The software description says it can geo-locate the wireless hacker from the traffic they send across the network, down to 2 meters accuracy. The software doesn't run as an executable in Windows,rather it needs to be burned to a CD, then used to boot the computer. The idea is, with your laptop (and the directional antenna on your wireless card), you'd walk around to triangulate the physical location of the Wi-Fi moocher.

you can find more about MoocherHunter via this link

this way you can locate the device with your laptop

Community
  • 1
Ashildr
  • 2,698
  • 5
  • 26
  • 45
5

Some wifi routers have a signal strength measurement on them. I know DD-WRT has this. If yours does, then you can do something like this:

  • Get a long Ethernet cord
  • Plug one end into the router and one into your cable modem/internet connection etc
  • Move the router around your apartment and see where you get the strongest signal

Keep in mind, water pipes/metal studs etc can all distort wifi signals

Another option would be to make your own directional antenna, kind of like this.

You could also check out this page for some useful command line linux wifi commands.

samthebrand
  • 340
  • 1
  • 4
  • 22
alexpotato
  • 153
  • 6
  • even if you cannot measure signal strength, you can (if you have a really LONG cable) move the wifi router until the device disconnects. If you get lots of interference from the neighborhood, it might not even be that far. – Mindwin Remember Monica Aug 09 '13 at 21:54
4

I was able to locate my device using horst on Linux. Other responses show how to triangulate, but not how to get the actual signal strength. horst can do that, and perhaps kismet, too.

First, run horst pointing to your wireless LAN adapter: horst -i wlan0. Then hit e to go to the ESSID screen and find your network. horst will find a bunch of devices from your neighbors, so you need to start filtering. From the ESSID screen, you can get the BSSID value for your network (the value within parenthesis) and restart with that filter: horst -i wlan0 -B xx:xx:xx:xx:xx:xx (of course, replace the xx with your actual BSSID).

horst should be showing now only your devices. You can now sort the list by signal strength (o then s), and walk around your house with your laptop, and see as the signal increases or decreases. The values are in dBm, so look for the number to increase (-25 is closer than -50).

If you're not sure which of the devices shown is your target, you have a few options. The simplest is to just switch down everything else: computers, tablets, phones and printers (I always forget the printer and keep wondering who's tied into my network). Another option is to run nmap on your network, and see if you can figure out which one is your target by looking at the provided information (for example, manufacturer can be shown, sometimes, given the MAC).

Once you determine which one is your device, you can restart with -e to look specifically at it: horst -i wlan0 -e xx:xx:xx:xx:xx:xx.

horst will only update the strength of the signal on the screen as the device sees traffic, though. You can try pinging it or talking to it (sending WhatsApp messages, for example). In my case, as I had already used nmap to find its IP and MAC, I found it easier to just put nmap on a loop scanning it (as ping would not do): while true; do nmap 192.168.0.10; done generated a fair amount of traffic to the IP, that allowed me to locate it just by walking around and looking at the signal strength. If you can't generate traffic on it, then perhaps you'll have to go the triangulation way.

caxcaxcoatl
  • 161
  • 3
  • 1
    That really did the trick for me. In my case there was a sufficient amount of traffic going on, and so the signal strength updated more or less in real time as I moved through the house, and was able to find the device in a matter of minutes. – pcworld Jan 21 '21 at 16:01
2

One-story flat? You can sort-of triangulate using signal strength alone. You have to assume that signal strength is proportional to distance from the transmitter, which isn't very accurate, but it could be accurate enough to help narrow down the search space.

  • Measure signal strength from 3 points in your flat.
  • On floor plan of the flat, mark your 3 points, and with a drawing compass, swing an arc across the flat with a radius proportional to the signal strength so that the arcs enclose a fairly small space within the flat.
  • If the assumption we made were true (and your measurements and drawing were accurate), your tablet should be within the space between the arcs. It's not quite true but hopefully not too far off either.
  • Start your search near that space. Hopefully its location will remind you of where you actually left the tablet. If not, search out from there, possibly repeating the above steps at a shorter distance from this location.

Multi-story flat? Same idea, only now you've got a 3rd dimension. Repeat the above on each floor. With luck, the signal strength will make it obvious which floor it's on. If not, at least you've narrowed your search space to a part of the house, even if you have to look on both (or several) floors in that part.

JRobert
  • 6,744
  • 24
  • 28