Ask HN: I just heard someone else's call on Skype | Hacker News Reader

Ask HN: I just heard someone else's call on Skype

28 pointscrixlet15 comments

This legitimately freaked me out.

I use Skype to frequently make calls to cells. I just fired up Skype this morning, dialed a cell number and hit "call". Then, without ringing or any delay I was suddenly on a call between 2 other callers. It sounded like a business meeting (talking about agendas, deliverables, etc) and the audio was a bit garbled with some type of distortion, but I could with some effort make out what they were saying.

Then they hung up and my call ended.

What happened here? Does this happen frequently?

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I have had this happen to me once. I am from India and we used to have this quite often when cell phones were just starting out, we even had a name for them - "cross connection". I could hear conversations but it happened only once. For what its worth, Skype tends to act up for me whenever there are rains in the location where I am calling to.

This is called "crosstalk". It used to happen in POTS reasonably often, and I have experienced it in mobile to mobile calls a few times as well.

Classical crosstalk on POTs is fairly easy to get your head around - signals from one circuit leaking out onto another circuit through EMI, e.g. wires near each other, faulty amplifiers etc.

I never came up with a good explanation for crosstalk in mobile (GSM, CDMA, ..)[1] etc as audible crosstalk doesn't seem to be possible at the radio level. In fact I would be surprised if the actual voice baseband signal is analog at any point on the network.

Nevertheless, it happens.

Most likely, you experienced crosstalk at the cellular end of your Skype call. In theory, barring some pretty severe software errors, VOIP or Skype crosstalk should be impossible.

[1] AMPS networks, sure, but the newer digital systems, no.

I had this happen to me 6 years ago in the U.S. on a cell phone. The only thing out of the ordinary was I was in a ship (not a cruise liner) at the dock with a bad cell signal at the time. I'm not exactly sure what happened then, but it was probably a "perfect storm" scenario for that to happen.

I noticed a load of icons downloaded to my Android Gallery application. They were not pictures I had taken, and didn't seem to be cached from something else I had looked at.

Maybe is an "IP conflict / IP duplication", and the VoIP packets go to both IP addresses.

IP duplication can be caused by some type of "monitoring/spy" at their (or your) computer, and a dynamic IP address.

it's not usual.

It sounds more like an issue at the POTS side of things.

It cannot be a "Plain Old Telephone Service" (or analog) issue, because it is working with "VoIP"-- and it's digital since the audio enter at the computer.

>"It cannot be a "Plain Old Telephone Service" (or analog) issue, because it is working with "VoIP"-- and it's digital since the audio enter at the computer."

Just because is entering digitally on your computer doesn't mean that it is completely digital. To make calls to a land line you still need a PBX in between to make the bridge between analog and digital sides

It's entirely possible that the "crosstalk" happened way before the calls every made it into Skype's domain. Skype will have a PBX somewhere that bridges the gap between Skypes IP protocol and the outside world of POTS and cellular calls.

sounds like user error ... in the form of interrupting local sound as sound pushed through a speaker

Not the case as I was in my home office which is... well.. silent :)

Still very strange. Shouldn't the calls be encrypted? If the other call was started before, and the OP's client wasn't there for the handshake, how could it decrypt the call content?

Still you encrypt the calls (the comunication line is encrypted)

The spy /monitoring software can be running at your computer --thing that is usual-- (so before encrypting...)

They don't need to broke any encryption ("NSA style"), only a "bug on windows"...

>"Shouldn't the calls be encrypted?"

Calls Skype to Skype are encripted, but as far as I know you lose that when you make calls to landlines or mobiles.

Not gonna happen with Sococo Teamspace. It uses unique encryption keys for every conversation, every pair of participants.

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