Tracing phone calls.

While watching a 1968 film, the police are trying to trace the phone call made by the murderer. OK, that was 1968. I see police trying to trace phone calls on cop shows today. Many times, there’s, “We didn’t have enough time” to trace it.

Can’t they trace phone calls easily today?

My assumption that every phone call is traceable even after the call is terminated. With each switching network handled by a computer, every phone office from the caller to the receiver would have logged the exact time of call, which telephone office the call came from, which computer it was routed to, and the desired ultimate destination. Now, it may not be instantaneous, (and it may take a few hours) but my assumption is that the call can be traced back to the originator if the receiver logs the exact time that the call was received. It wouldn’t surprise me that each telephone switching computer retains the last few hours in memory so that the phone company can instantly trace a call.

The only exception would be burner cell phones. Even then, and even without GPS, they would probably be able to pinpoint the location within a mile if the cell phone was within range of two or more towers.

So, is the drama of “Trace this call” on police shows just drams?

Tracking a landline is immediate. After all the callers number will appear on your phone if it’s not withheld. If it is, the telephone company can still find it in seconds.

Using a ‘burner’ works but the crooks need to get away fast as the cops can see where it is pretty quickly. The trick would be to use it in a moving car (making sure that there is no CCTV around) and then chuck it on the back of a passing truck.

Internet is better - using Tor, you might not be able to hide from the NSA, but it’s pretty hard to trace.

Wrong. Caller ID is trivial to spoof.

Computersied phone exchanges only came in in the mid 70’s. And even then they took quite some time to replace the older mechanical ones. New exchanges would have a computerized exchange, but until there was both need and funding for a refit, older mechanical exchanges would remain.

When calls were restricted to telco infrastructure it would be difficult to avoid tracing - but as the phone phreakers discovered, the use of in-band signally between exchanges meant you could spoof things, and the records would not be correct, or not even exist.

Now, with more and more voice being reticulated on IP, it is getting harder and harder to work out the path a call takes. Whereas records might exist (and the level of logging that can take place is much greater than people realise) the records can be widely distributed across many telcos and internet providers. When the path goes international it gets even worse. TOR probably adds far too much (and uncontrollably variable) latency to let a voice call work. But without going to all that trouble a VOIP initiated call may be desperately hard to trace. As noted above, the actual ID on the call can be spoofed to anything you like.

Around the 1980’s I recall reading that the more modern switches had a mechanism for “locking” a circuit open to facilitate tracing. tracing consisted of chasing a circuit from mechanical switch point to mechanical switchpoint until it disappeared into a trunk line to another exchange - then calling the people there and telling them which trunk line to start from.

The amount of time in movies was purely arbitrary, but the ability to immediately trace a call didn’t come into existence until the exchanges were computerized.

mc2000 – they had set that up in the 80s so that you could dial a number during the call to keep it open. It was used for people who complained about obscene or harassing phone calls.

I use Verizon as my call provider. With Verizon, I can request that a call be traced immediately after the call ends. Apparently this feature is meant for reporting abusive or otherwise illegal phone calls. I just hang up the phone after the call ends, then pick it up again and dial *57. The call is traced and the information sent to my local law enforcement agency (note: not to me - information about the caller is not mine to possess).

I don’t believe that callerID info (which, as many folks have mentioned, is easily blocked or spoofed) is involved as part of the tracing process.

Rachel at Credit Card Services has been calling me regularly for over ten years, and nobody has found a way to trace her calls yet.

I realized sometime in the last year or so that Rachel had quit calling me. I’ve been concerned that something might have happened to her.

LUDs. It’s all about the LUDs.

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