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What Does It Take to Track a Million Cell Phones?

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Re: What Does It Take to Track a Million Cell Phones?

#41

Post by Evelyn656 »

mikepurvis wrote: post #38
strictnein wrote: post #29

This article finally answered a question I've had for a while: how they can do decent triangulation with just two towers. > "We said that a tower covers a radius around it. In practice, this is sub optimal so that’s not how it’s done. > Instead, a station is usually split in 3 independent beams of 120 degrees." So it's not the intersection of two circles anymore, it's the intersection of two arcs, which will likely o…

Sometimes it's split even more: https://www.google.ca/search?q=sector+antenna&tbm=isch

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Re: What Does It Take to Track a Million Cell Phones?

#42

Post by aembleton »

gvb wrote: post #36
losteverything wrote: post #18

If my phone is powered off can i be tracked? What if i remove the battery?

If your phone is powered off or in airplane mode it is not supposed to emit RF and thus cannot be tracked. This is a matter of trust, so if your threat model includes high end threats, the assumption that it follows the normal requirements may be invalid. If you remove the battery, it will be unpowered and unable to emit RF and thus cannot be tracked. While it is theoretically possible to hide an auxiliary battery in…

Modern thin phones don't let you remove the battery, so they could easily continue to transmit RF.

Re: What Does It Take to Track a Million Cell Phones?

#43

Post by frandroid »

jandrewrogers wrote: post #39

I've designed systems that do this on continental scales (i.e. hundreds of millions of cell phones simultaneously, in real-time). The devil is in the details and non-trivial; this is not a "an intern and 6 months" job. Mobile telemetry is not nearly as ideal in practice as assumed here and it typically takes a couple years to learn how to handle the numerous peculiar artifacts of that data that will damage the qualit…

Have you posted about this at length somewhere? If not, care to elaborate on what it took to design this system?

Re: What Does It Take to Track a Million Cell Phones?

#45

Post by mostlyskeptical »

strictnein wrote: post #29

This article finally answered a question I've had for a while: how they can do decent triangulation with just two towers. > "We said that a tower covers a radius around it. In practice, this is sub optimal so that’s not how it’s done. > Instead, a station is usually split in 3 independent beams of 120 degrees." So it's not the intersection of two circles anymore, it's the intersection of two arcs, which will likely o…

A step beyond that: some can get fairly accurate with a single "tower". We had at minimum 3 BTS on every site, generally at 120 degree spacing but this could vary, but each BTS had multiple antennas and would do some rudimentary triangulation based on signal arrival times to each antenna. We could generally get within a couple of hundred fee.

Re: What Does It Take to Track a Million Cell Phones?

#46

Post by monksy »

jimktrains2 wrote: post #5
warrenm wrote: post #2

The phone companies already do this, more or less, as is shown in court cases where cell phone records are brought in as evidence A decade ago that data was a little more iffy (i.e. it was more a good estimate (typically within half a mile or less) than a true location), but with a combination of more towers (and therefore more data points), the ubiquity of smartphones (which check in more often, are doing geolocatio…

> The phone companies already do this, more or less, as is shown in court cases where cell phone records are brought in as evidence You can also arrange to buy this information. I worked for a place where you could request someone's location by phone number. There were a lot of contractual obligations around us having the phone owner "allow" us to do that, but no technical ones.

Yep this is more than possible. It's done in marketing. If you have a short code to "text for coupons" There's a high chance that they're doing a ping against your number.

Re: What Does It Take to Track a Million Cell Phones?

#47

Post by jandrewrogers »

frandroid wrote: post #43
jandrewrogers wrote: post #39

I've designed systems that do this on continental scales (i.e. hundreds of millions of cell phones simultaneously, in real-time). The devil is in the details and non-trivial; this is not a "an intern and 6 months" job. Mobile telemetry is not nearly as ideal in practice as assumed here and it typically takes a couple years to learn how to handle the numerous peculiar artifacts of that data that will damage the qualit…

Have you posted about this at length somewhere? If not, care to elaborate on what it took to design this system?

I have not written about it. Most of the difficulty and complexity, from my perspective, is in the data science and processing required to construct an accurate population model, which requires additional data sources beyond the mobile telemetry. I designed the custom database platforms (easy for me) underneath which supported the online data processing.

It isn't that difficult technically, if you have experts doing it, it just requires far more domain expertise to do correctly than I think people expect. You also need to be willing to write some of your own tooling to deal with the data efficiently and effectively.

Re: What Does It Take to Track a Million Cell Phones?

#48

Post by rsync »

Rjevski wrote: post #3

Note that a lot of the information from the BTS is already available to anyone who "asks nicely". The mechanism that provides roaming is based on trust, so anyone connected to the SS7 network can query the location of any phone in the world and even intercept its calls. Just say to the home carrier "hey this phone is roaming on my network, would you be able to send me all of its calls and texts?".

"The mechanism that provides roaming is based on trust, so anyone connected to the SS7 network can query the location of any phone in the world and even intercept its calls."

One of the first things I did after opening the article was to search for the string "ss7" ... was disappointed to see it mentioned zero times ...

Re: What Does It Take to Track a Million Cell Phones?

#49

Post by rsync »

liprais wrote: post #40

this method will only work with GSM network because 1.GSM networks doesn't verify BTS 2.GSM encrypt keys are cracked and all over the internet. Users of other kind of networks should not worry about this kind of hack. Actually here in China a fake BTS a.k.a 伪基站 can be easily purchased online.

"this method will only work with GSM network because ..."

Yes, that's true - but remember that all of our 3G/4G phones are also 2G phones and that if you disable/jam/overpower the 3G/4G signals the phone will very happily revert down to 2G, possibly with no encryption, and possibly in a way that you have to be very careful to even notice.

There are quite a few attacks that are mitigated by 3G/4G in theory, but in practice you're still vulnerable to because your phone can be downgraded to 2G by an outside actor.

Re: What Does It Take to Track a Million Cell Phones?

#50

Post by detaro »

freeflight wrote: post #7
nawtacawp wrote: post #6

Earlier quoted context omitted.

There was a talk/demo I saw a few years ago that went into great detail about how this works. I remember it was given by a German. Anyone know what I am talking about? Edit: It was a video.

I remember something similar, it was a presentation given at CCC in Germany. Tried searching for it on their YouTube channel, just to discover said channel was terminated for breaking YouTube ToS?! That's really sad, their channel had videos of all the past talks from the CCC, an amazing resource that's now gone. I think this is the one you might have been talking about: https://www.youtube.com/watch?v=lsIriAdbttc If…

You probably were thinking of the CCCen YouTube channel? That never was an official channel, but a copy-cat that just uploaded all the CCC stuff, and was banned for it.
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