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Comment by nemothekid | Hacker News Reader

>If you call a landline, it’s up to you to end the call. If the other person, the person who receives the call, puts down the receiver, it doesn’t hang up the call, meaning that when I went to find my bank card, the fraudster was still on the other end, waiting for me to pick up the phone and call ‘the bank’.

Can someone explain this? This seems like a pretty glaring and obvious issue that I'm sure I would have experienced before. Is he saying that if he hangs up the phone and picks it up again and the person at the other end doesn't hang up, then the conversation isn't over?

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It's a well known tactic used by scammers in the UK.

(https://news.ycombinator.com/item?id=4825751)

(https://news.ycombinator.com/item?id=4826367)

Here's another newspaper article about the scam. (http://www.guardian.co.uk/money/2012/may/23/credit-card-user...)

EDIT: cultural note - we don't[1] pay to receive a phone call, even with cell phones. Perhaps that makes a difference?

[1] Well, with normal accounts that is. Obviously free-phone 0800 numbers etc are different.

My landline phone (BT 6500 Cordless Phone) rings if you have hung up but if the person on the other line hasn't hung up after 5-10 seconds which is great if you accidently turned off the phone (my parents do this all the time) and in this instance for this case.

As I understand it, it's some of the insane backwards compatibility the 'pots' system has to put up with.

If you think way back, before dtmf/touch-tone phones, when you dialed a number, the line clicked. You press one, the line clicks once. For zero, 10 clicks. This is backwards compatible all the way to rotary phones.

Those clicks are the line being closed and re-opened in rapid succession. You dialled by 'hanging up' repeatedly. So the line can't close the moment you hang up - there's a grace period while it waits for the next click. If the initiating party does't hang up, they emulate this grace period until the exchange times out.

That is true, but it doesn't require more than a couple of seconds. I used to dial by hanging up when I was a child, even in modern DTMF phones.

Ever see the "flash" key in a phone? Add a few milisseconds to that and a modern phone system should hangup.

That's the problem; it's not a modern system. eg, the British GPO 332 handset was first issued in 1937 - and still works. It's difficult to demand millisecond timing when you're backwards-compatible with pre-war equipment.

Way back... I still use a good old GPO rotary phone. Only thing you sometimes have to retrofit is the capacitor on the ringer circuit, as they're usually dead, or not big enough for today's lower voltage lines.

I seem to remember a case, possibly in Sweden in the late 90's or early 00's, where a woman was unable to call an ambulance for her husband who was having a heart attack, because of an incoming caller who had not hung up properly (or something along those lines). After some panic I think she ran to a neighbours house where she was able to make the call.

If I remember the story correctly, this resulted in some debate followed by a law change, such that now if the called party hangs up, you have only a few seconds before the connection is broken.

I don't know how it went for the husband though...

In the UK if the person on the other end hasn't hung up and you dial 999, the call ends. It's the only way I know to force-end the call.

It seems so backwards! Why wouldn't you be able to hang-up if you are the callee? Anyway, it makes it clear now how the scam works.

In a proper telecom setup, if the hang-up time is longer than the flash time (a few hundred milliseconds) then the call should end - period. This allows you to hang up properly while allowing for call waiting features and the like.

Phone systems allow this so that the called party can answer on one handset and then easily transfer to another handset on the same line by hanging up the first and picking up the second handset within a certain duration. In Australia, IIRC this is around 45 seconds. I'm not sure if this is universal. It's certainly unnecessary for mobile (cell) phones.

I believe it's 90 seconds in Australia.

I've not observed this at all, it must only happen with some exchanges. For me when the phone is hung up, that's it.

For A29 and other analog PBX this is the default behavior. It is the way the relay based operate.

Are there even any of them in use? I was talking to a Telstra employee a few years ago who mentioned that there were only one or two in country towns that didn't warrant replacement.

It's also great for setting up three way phone calls. Man, just had a flash back to primary school!

I've seen that happen in the U.S. too: if one of the parties doesn't hang up, it may take quite a while for the connection to time out.

In the U.S., as soon as the caller hangs up, the call is disconnected. There's a delay only after the callee hangs up.

US Phone system worked this way at least when I was younger; there was a party trick you could do to have someone call your phone, hang up and then tell people to "pick any name and I'll call someone with that name" then pretend to dial and ask for that name, your friend says something "Yes, that's me, who are you?"

Wouldn't that trick work equally well by just learning your friend's number and actually dialing it? I don't see where the phone thing comes into play here.

The name is chosen by someone who isn't in on the trick.

> then pretend to dial and ask for that name, your friend says something "Yes, that's me, who are you?"

As long as I tell my friend "I'm going to call up, pretend you are whoever I ask for", then when I call up and say "hello is Mr X there?" it's irrelevant whether I just dialed my friend, or whether he was sat on the line waiting for me to fake dial.

You've missed the point of all of this.

The person being duped provides a name and a number.

You leave your line open with a friend. Then you dial the new number, which doesn't work because the line is open, but it appears to work, fooling the person being duped.

Dialing the new number is a required part of the illusion so the person you are duping believes you are calling the person they provided the info for.

If you just dial your friends number and don't use the fake number... and they see you doing that... then that's stupid and your friends would have to be exceedingly trashed to fall for what is essentially you just dialing a friends number and talking to them.

Where does the person being duped get the number from? I thought the whole point of the trick was that they would give you a name and you'd come up with a number for it.

The trick is that you (or even the audience) actually dial Mr. Smith's number in front of them. The trick is no good if you dial your friend's number openly.

Yes, that's what happens here in Australia (and I assume the UK). If the receiver doesn't hang up the call disconnects. The exchange disconnects the call after 1 or 2 minutes.

What I don't understand is how the scammers got his landline number?

If it's a listed number, you can just look it up in the phone directory if you know the name and address.

Have we forgotten phone books so quickly?

Phone directory = phone book, I'm not sure what your question is.

Is this a UK versus US thing?

Followed him home, then used a phone number search? That would also explain why they didnt need to ask him his address.

This is a really elaborate scam, btw. The few times my cc# has been stolen, some dude just makes a card and uses at someplace like a hardware store and buys $1500 worth of tools before the bank frauds it out. In, out, no contact with me, just a sprint.

In the european chip and pin system, there's no way to extract the private key on the chip - the chip has to be present, and has to be unlocked with the PIN. Which is why they had to steal the card, and get him to enter the PIN. (of course it's possible to trick most merchants to fail back to the legacy mag stripe which is still present, but perhaps that triggers fraud alerts quicker)

I see a lot of "yes, that's how it worked/works" answers from Australians and people from the UK.

Maybe to add a little bit of diversity:

At least in Germany, I don't recall this ever working.

It used to work with analogue lines, but I'm not sure wether it still works with the digital ones that most people now have.

Just want to chime in that it used to (and still does, I think) work that way in Belgium for classic landlines.

Perhaps it works that way in the UK? Seems odd to me as well.

It lets you do things like receive a call, put the handset down (or even unplug the phone!) then continue by picking up a phone on the same line in another room.

It also meant you would accidentally DoS someone by failing to hang up correctly if you initated the call - the pre-mobile equivalent of someone phoning you from the inside of their pocket...

Many years ago, when I used to drink (far too heavily on this occasion) my last memory of an evening was ringing up my Godmother to see how she was; powered by a kind of drunken momentum to say hello to someone I love.

I didn't remember anything about the conversation, only that I got up from bed with a pounding headache and thought no more of it. A few days later my godmother phoned me up:

"Do you remember what you did a few days ago?"

"I think I phoned you up?"

It turns out that while she was talking at length I had passed out from the booze. She had spoken for some time and then I hadn't replied. After some time, finding the call strange, she hung up and picked up, only to find the sound of silence; my room in which I had passed out. This was unfortunate as she had quite a few phone calls to make and she was effectively blocked from doing so. Presumably at some point I came back to some kind of consciousness that was capable of putting the receiver down and staggering to bed, but not capable of remembering. Thankfully I was forgiven and suffered only the punishment of wry disapproval.

So yes - as a young man I accidentally DoS'ed my Godmother because of stupidity and Stella Artois.

I believe this was alo used by hackers/crackers back in the modem era. When you connected to a corporate system the system would first identify you, then drop the connection and call you back to your official number. If you did not hang up, the system ended up connecting back to you.

We used this technique all the time in India to fool our parents, :P

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