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Tuesday, April 17, 2012

Not all telco knowledge is used for phreaking

Sometimes I get looped in to troubleshoot systems which are far away and are being run by companies where I have no connection to anything inside. Ah, the joys of helping family.

In this particular case, there's someone in a certain part of the country who was unable to receive calls from other family members a couple of days ago. Her land line could place calls, but receiving calls from certain people did not work. They originally thought it was something crazy involving her actual physical line, but that was before they got me involved. Obviously, if she had dial tone and could call people, it couldn't be that.

So I decided to come at it from the other side. People who were having problems would dial that number and it would just hang there, with no sound at all. After an unusually long amount of time, it might make a busy signal or a reorder tone ("fast busy").

I found it interesting that this would only happen when certain people called from specific lines. If they used their cell phones, then it was fine. Two different "land lines" from two different cable companies hundreds of miles apart both exhibited the same problem.

It was time to do a little troubleshooting. First, I had one of the affected callers dial 1-700-555-4141 to see if that little readback still worked. It did, and it confirmed that she was with such and such cable company for long distance. Then I had her try the equal access "dialaround" thing, forcing it through AT&T with 10-10-288-1-700-555-4141. The message changed to their little blurb.

Now that I knew both who the default carrier was and that dialaround would work on that line, I had her try a straight "1+" call and note exactly what happened. It did the "long delay and then busy" thing as before. Then I had her immediately hang up and try to force it through AT&T : 10-10-288 + the original number.

It worked.

That was all I needed to hear. Any sort of crazy "call blocking" service on the receiving end would have behaved the same way regardless of who was delivering the call, since the calling number was unchanged. This told me it was something to do with whoever was transporting the calls to that area and their connection into Verizon (the destination telco).

Armed with that information, calls were made to various telcos. They relayed exactly what they had tried and what changed. The telco people were astonished and understood what it meant.

The next day, all was well. They called it a "one in 500,000 customer event". Maybe that means "one in half a million customers knows enough about the system to try this sort of thing".

There was one disappointing part to all of this: the affected callers with Comcast's Digital Voice product were unable to do any dialaround tricks. It's their way or the highway. Also, the 1-700-555-4141 thing does nothing on there, probably for similar reasons. I didn't know it was possible to sell phone service in this country without this kind of "equal access" support, but they obviously found a way.

That's my life: applying arcane bits of knowledge to help people.

What can I say. I like it.