Time to Trace Phone Calls?

A little background information as to why I’m asking this question. No, I’m not trying to evade the police/FBI/CIA and I’m not trying to trace other people’s phone calls.

I watched the Bourne Supremacy the other day, which is a very good movie, but in it they utilize phone tracing to locate Bourne, as they do in almost every other movie. Typically, it takes XX seconds for them to confirm a positive location as to where the perpetrator is. However, I was thinking that when you make a phone call it actually logs the call time, place, and destination instantaneously when it hits the phone companies switchboard, and with the proper connections, a trace could be almost instantaneous. That is unless you somehow routed your call through different stations around the world…

I suppose the question is, how feasible is it for them, being police forces, to trace phone calls in certain periods of time? Is it true that it requires so much time, and what determines how much time it actually takes?

Tracing is instantaneous these days. The movies just keep it up for dramatic purposes.

The Bourne novels are roughly a quarter century old. Caller ID (and the technology to support it in widespread fashion) is barely a decade old–and was not implemented uniformly when it was developed. I suspect that future novels and movies set in the period after, say, 1997, will no longer use the “xx seconds to trace the call” plot device, simply because it will make no sense to the audience. I have not seen the Bourne movies, but if they were not “moved up” to be current (i.e, if they are still presented as Cold War stories), then Caller ID is a future event (much as cell phones and similar devices) and call tracing is still limited to the late 1970s technology.

A few years ago my grandmother died, and when I called the police to report the death, they already knew my location and name…less than ten seconds after the call went through.

Unfortunately, they were still using this bit in the most recent season of 24 (which ostensibly takes place in 2008).

Just FYI…if you press *69 on your phone it will give you the last number that called you. I assume that most phone companies have this feature.

Somehow I’m not surprised that screen writers get so wrapped up in old “standard” devices that they use them after they have become obsolete. I made a 911 call from a cell phone, this summer, and was redirected to the correct police department (in a rather large county, calling from a phone with an area code two zones away) as soon as I said the word “accident,” but the world’s most sophistcated super spy shop can’t trace a phone call from a land line. Hokey-dokey.

I you called 911, there is a special feature involved in 911 calls. The telephone switch sends the ANI / ALI (automatic number identification, automatic location identification) to the closest 911 answering point in your neighborhood. As soon as they pick up the call (within a couple seconds), your name, address and phone number are displayed.

What if you say routed your call through various switch boards in multiple countries, granted that you had the know how to do so in the first place. Still instantaneous, or would there be a time lag?

I also thought that there was something to do with tracing cell phones to an exact location that you need to triangulate the position based on the time it takes for various receivers to acquire the signal.

Could the “time” they are referring to be the time it takes to triangulate the exact position?

I’m going to jump in here as this is one of the few questions that I can answer from knowledge rather than a wild guess.

As other people have mentioned phone tracing is (mostly) instant nowadays. When I make a call to someone my number is passed through the network until it reaches the final exchange before my destination. The final exchange decides if that information should be passed to the person I’m calling (i.e. do they have caller id, do I have id restriction, etc). Therefore even ‘withheld’ numbers get passed through the network – they’re only withheld at the last minute.

If the last stage is a telecoms company or a police station or something then they can get access to the number. For example the company I work for owns the equipment doing the ‘last stage’ and I can get the number of any call coming into the company even if the caller withheld their number.

A fixed (non-moblie phone or premium rate) number will be enough to uniquely pinpoint a location.

Life is not always that simple however …

You’ve identified a couple of potential workarounds.

  1. Route the call through a network incapable of passing your original number through it. I.e. an older foreign network that doesn’t propogate the calling number or various new internet based networks which also don’t always preserve the number. Then the call completes with an ‘unknown’ number at the other end. To trace this call you’d have to start looking at the messages that were sent to establish the call and working back to the point where the number was discarded. This is easier when the call is going on as there is a link between the calling and called parties. I would guess it’s still possible after the call as, legally, telephone companies have to be able to provide this information.

Of course, if you pass it through a network in a country that’s unable or unwilling to assist then you’re probably home free. However, there’s no real way to do this short of getting someone in that country to set up someway of calling through them (call forwarding may not be enough as in some cases the forwarded call will be established from the original calling country and not passed through the forwarder).

I should note that some networks will not accept calls with no number, but that’s not too common. It’s more common that companys (rather than networks) will not accept calls with no number (but will accect number withheld calls).

  1. Use mobiles. Mobiles are locatable but it will take more time. Recently the US started to insist that mobile calls are locatable for emergancy purposes (not sure if that’s law yet but it was a big thing when I worked on the mobile side of things). When you make a mobile call your phone talks to the nearest receiver and the call continues as normal from there. So your number can pinpoint your mobile provider and your mobile provider should be able to check which receiver you’re communicating with. But that only narrows you down to a cell, it a city that can be a few blocks in the country it can be a good few miles square (well actually it’s a hexagon on most diagrams but lets not get into that).

Mobiles are locatable because other receivers in other cells can also hear your phone but they’ve communicated with their neighbours and they know they’re getting a weaker signal so they’re only listening in case the signal gets stronger and they decide to take responsibility for the call. Therefore to locate a mobile call you find a couple of receivers nearby to the ‘in-charge’ one and the relative signal strength do a fancy single-strength-triangulation calculation and you can pinpoint somebody to within a few meters.

The actual area pinpointed depends on the size of the cells, so in a city you can get within a few feet, IIRC in the country it can be a 10 meter square or so.

Before the goverment stepped in to insist on this it would be conceivable that this would take some time to do. Nowadays it should be instant (plus mobile location technology is big money – call for exact directions to your nearest Pizza Hut, etc).

There’s one more idea … (hopefully this is in the realms of technicalities enough to not be illegal advice).

  1. Lie.

Earlier I said that normal calls propogate the calling parties number across the network and that the ‘last stage’ of the system sees this number regardless. If you have access to this last stage and start a call from there then you can send any number you like – if people aren’t paying attention they’ll ‘trace’ you to that number. They’ll realise their mistake and maybe be able to pull the real location from the telecomms companies logs but by then you’ll have escaped.

How can you do this ? Until recently you had to work for a telecoms company, but now the internet and the telecoms world are converging, so you can call through the internet to a real-world phone. If you know what you’re doing you can spoof you’re outgoing number as simply as people fake e-mail addresses.

Of course with internet telephony a phone number (even the real one) will only translate back the provider for that service who will, at best, be able to match it up to an IP Address and whatever details you supplied when you registered the account. If you’re account details where fake or stolen then all you have is an IP Address. Tracing IP Addresses is practically impossible if your tracee knows what they’re doing and would certainly take too long for it to be useful. For example, criminal uses stolen details to register for an internet phone account, sets up the software on a public library computer then makes the call through an anonymous IP Proxy. I’d be impressed if someone could pin that call on that criminal.

Expect this to be a major problem over the next five to ten years ( internet telephony will bring back a resurgance of the '80s phone phreaking craze – you heard it here first kids ).

Bottom line: Movie phone tracing takes time for dramatic purposes, it used to take that long. It doesn’t any more. In a few years sufficently sophisiticated criminals will be able to place calls in such a way that it will take time to be locatable and I’ll give kudos to the first movie to do that correctly.


Phone geek. And this is my 200th post, yay. 3 years, 200 posts and this is the first really useful one.

It is law, AFAIK, but the networks haven’t caught up yet. My phone can receive and forward GPS info, but none of the towers around here know what to do with it.

In the US, with CDMA being the dominant system, a phone might be communicating with 3 or more towers at once, so there’s even less detail. I’ve heard that it’s also a lot harder to triangulate the position of a CDMA phone because of the tight power control.

Unfortunately that hasn’t really taken off here either… yet. :frowning:

May not work if Caller ID is blocked.

With a court order law enforcement can get phone co. records for specific phone no.s and time periods.