When you use a free 2nd line on your phone - how can they trace it back to your "real" phone number?

That's an error. Using a primary phone and associating it with a "2nd-line throwaway".

The "2nd-line" must have an association with a primary phone number to function, hence there are a multitude of "temporary" records created in numerous places most would never consider. The only assurances you have are with the party providing the temporary "2nd-line". Those assurances don't extend to other carrier parties once communications leave the point of initial entry.

Also, governments monitor cellular calls and look for frequent patterns involving specific numbers. One or two random calls may disappear in the billions of calls made each day, but regardless of any anonymity claims made by a provider of throwaway numbers, a call was made and a record established. EMC ($torage) and Ci$co (Buggy network equipment...) are both participant$ in this deception.

Someone would have to be interested enough to look for the transaction and work backwards from the endpoint.

Did you create interest?

Nomen Nescio snipped-for-privacy@dizum.com asked

I'm searching for where that (public?) database query lies...

Is it something secret? Hidden?

Where is this database located and who populates it around the world?

Why? It's of no use to you. Those databases are for operational use by phone companies.

SS7

scorpion snipped-for-privacy@dont-email.me asked

I'm not worried if they trace it. I'm just trying to figure out how they trace it.

For example, sometimes when you use the 2nd line for a web site account authorization, they seem to KNOW it's a 2nd line. But other times they don't care.

But for the ones who know it's a second line, how do they know?

Yeah. But where? Are those 2ndLine-to-RealPhone indices accessible to we mere mortals?

I'm not aware that the 2nd-line cellphone apps assure you of anything.

I'm sure they'd be bored to death tracking my phone calls. But that isn't the question of whether or not they'll be bored.

The question is how can we find these tracking sites they may use?

Nomen Nescio snipped-for-privacy@dizum.com asked

Many sites nowadays ask for a phone number to verify with a text. I give them always, first, the 2ndline numbers. Somewhere roughly around half the time that bogus 2nd line works. I get the confirmation text and I can then register the web account.

For the half that work, I don't care why they work. Because they work. For the half that don't work - I'm curious HOW they knew it was a 2nd line?

More to my needs, I'd like to know how to tell what the lookups say for my

2nd lines as I'd like to expand my use of the 2nd lines to times when companies ask for my phone number and I don't feel like arguing with them.

I googled to find that SS7 is most likely "Signaling System 7"

"SS7 separates signaling from the voice circuits." "The SS7 protocol stack may be partially mapped to the OSI Model of a packetized digital protocol stack."

Apparently whatever SS7 is, it's extremely vulnerable "In 2008, several SS7 vulnerabilities were published that permitted the tracking of cell phone users.[14] In 2014, the media reported a protocol vulnerability of SS7 by which anybody can track the movements of cell phone users from virtually anywhere in the world with a success rate of approximately 70%"

It seems to have holes everywhere "SS7 vulnerabilities had been exploited to bypass two-factor authentication to achieve unauthorized withdrawals from bank accounts."

But I didn't want to get into how secure or insecure SS7 is.

Maybe I should have asked the question differently. Q: How do they know that I'm using a 2nd line?