There's a saying in tech: "If the product is free, then you're the product."
Here's how most Internet companies work: If your app is free, then they are selling your data.
If your ad blocker is free, they are selling your data.
If your VPN is free, they are most definitely selling your data.
Can you blame them? They have to turn a profit and there are many, many companies who will buy a file containing the browsing habits of millions of people.
The only way they can sell that product is if they log your information.
I know because I've worked with these companies for many years. They all start out with some simple information: IP address, timestamp and the URL you visited. That's not so bad.
But competition is fierce and the bar is constantly being set higher. So in order to sell to bigwig ad executives, they have to keep up and even stand out. So they start augmenting that file with things like your zip code, your marital status, your income, what kind of music you like, hobbies, the number of children you have and so on.
You probably know that every website you visit on your cell phone is being recorded by someone.
But did you know that right now there are companies collecting your Amazon shopping cart data? That Google is buying your store receipts from Walmart? And that your antivirus software is secretly collecting your data, too...?
All of this data is being traded and collected in clumsily constructed data warehouses called "DMPs". That technically stands for "Data Management Platform" but you can think of it as "Digital Monitoring Platform" because they all assign a unique identifier to you, your spouse and your kids, and sometimes to each of their devices as well.
Marketing agencies don't have high margins and they aren't security experts, so anyone with the right credentials (and often without any credentials at all) can tap into this firehose to learn personal details about your private life that you would rather they didn't know.
Governments can subpoena this data and hackers are now targeting it as well.
The only way to prevent it is to not collect it at all.
And because our product isn't free, you can rest assured that you aren't the product.