How can a number be determined by a digital trace?

Question

JavaScript

Good afternoon
Today, on one of the sites I saw an advertisement, determining your visitor's phone number.
The question immediately arose, how?
Here is what the service itself writes:

How it works?
The digital trail service identifies the phone number and puts it in your personal account with a detailed dossier, it becomes possible to advise visitors before they go to competitors

Now the question is for those who "fumble", how does this really happen?

Answer 1

It all started with the fact that the VK pages began to burn at the entrance to the site. Thanks to the jambs of VK.
From there they pulled the "dossier".
Gradually, the screws were tightened in VK, the last time of 2-3 years they tightened it so much that it died or almost died.
Maybe they came up with another bypass, but then I didn’t master it and scored, I didn’t really need it anymore.
Now they most likely work simply according to the scheme of collecting data from the sites on which the service is used and sharing them between the clients of the service under the sauce that they can get any data at all.
Those. the more sites use this service, the more likely you are to get information about your visitors.
When you enter any data on site-1 with the service, the site saves them.
Then when a visitor gets to another site-2 using this service, we immediately get his data that he entered on site-1.
Or they break through the already assembled base if they can and show you the info. In my database, for example, 3+ million VK profiles collected in this way, I think that there is some kind of success rate if you try to calculate visitors to any sites from it.
Summarizing the above:
There are ways, of varying degrees of lousyness, but everything directly depends on the method of collecting information and the amount of traffic passing through the service.
But the texts, of course, are as convincing as possible that in general all visitors will be collected, of course, lies.
At the best of times, data from 25-60% of visitors from site traffic was identified. It's probably much less now.

Answer 2

Today I saw an advertisement on one of the sites

Very simple - nothing.
You are just a gullible person.
What you are being sold is complete nonsense and only those who believe in the "digital footprint", Freemasons and reptilians peck at it.
In short, do not be fooled, this is a scam in the spirit of "read other people's sms" - you will simply be thrown off a random selection of pre-prepared templates.
"With a detailed dossier", lol, and surely there will be a sucker who will incur money for them.

Answer 3

Most likely it means that the user's history on the Internet is parsed. Where and what forms he filled out, perhaps social networks get there too. If once a callback was ordered on some site, your data can go anywhere.

Answer 4

Well, how, how ...
"Hello, they call you from the security service of Sberbank ..." (C) And then the Lokhov divorce begins, as a result of which the sucker himself must withdraw all the money and transfer them to a certain account in a certain bank :)
Here so they will immediately sell the "service" and even examples from the "personal account" will show :)
PS: But this is all garbage. We had an announcement at the entrance about the fact that "invisible laser inscription of the TIN" will be made on the forehead: D