That phone number field in the signup form seems harmless enough. Type in ten digits, receive a verification code, and gain access to whatever service prompted the request. Most people don’t think much about what happens next. The number disappears into a database somewhere, presumably sitting there unused unless the service needs to contact the user.
That’s not quite how it works. Phone numbers become active data points the moment they’re submitted, traveling through systems and processes most users never see or consider.
The Immediate Database Entry
First stop is the company’s user database, where the number gets stored alongside other account information. This seems obvious, but it’s worth understanding what “stored” actually means. The number doesn’t just sit in isolation—it gets linked to email addresses, names, payment information, usage patterns, and any other data the service collects.
These links create a profile that’s more detailed than any single piece of information suggests. The phone number becomes an identifier that ties together everything the service knows about the user. When that database eventually gets breached (and many eventually do), all those connections leak together.
Database security varies wildly between companies. Some encrypt phone numbers and protect them carefully. Others store them in plain text with minimal security. Users have no way to know which approach a service uses until a breach happens and the details become public.
The Marketing Department Gets It
Most services feed phone numbers directly into marketing systems. This isn’t necessarily for immediate spam—though that happens too—but to build target audiences for future campaigns. The number gets tagged with information about what the user signed up for, when they joined, and how they interact with the service.
This data helps companies create “lookalike audiences” for advertising. They share hashed phone numbers with advertising platforms, which match them to profiles and find similar users to target. The original user might never receive a marketing text, but their number helped identify thousands of other people to advertise to.
Some services explicitly state in their terms that they’ll send promotional messages. Others bury it in privacy policies that nobody reads. Either way, providing a phone number often opts users into marketing contact they didn’t clearly agree to.
Third-Party Sharing Begins
Here’s where it gets complicated. Many services share phone numbers with partners, vendors, and affiliated companies. The privacy policy might mention “trusted partners” or “service providers,” which sounds limited and controlled. In reality, phone numbers can flow to dozens of other organizations.
Payment processors, analytics companies, customer service platforms, data enrichment services—all might receive phone numbers as part of normal business operations. Each recipient adds that number to their own databases, creating more copies in more locations. Each copy is another potential breach point.
Some of this sharing happens automatically through integrations and APIs. The service doesn’t manually send phone numbers anywhere—their systems just sync data between platforms as part of how modern software works. But the result is the same: wider distribution than users expect. This is why many people now use a Virtual Phone Number for signups, keeping their actual number out of these distribution chains while still getting the verification codes services require.
Data Brokers Enter the Picture
Phone numbers often end up with data brokers, companies that collect and sell information about people. Sometimes services sell directly to brokers. Other times, brokers acquire data through partnerships, breaches, or by scraping public information and matching it to phone numbers.
Data brokers combine phone numbers with information from multiple sources to create detailed profiles. They know the number, who owns it, where they live, what they buy, what sites they visit, and more. These profiles get sold to advertisers, political campaigns, background check services, and anyone else willing to pay.
This is where spam really accelerates. Once a number reaches data broker databases, it’s available to a wide market of buyers. Each buyer might generate calls, texts, or other contact. The connection between “signed up for one service” and “receiving spam from dozens of sources” isn’t obvious, but it’s direct.
The Alternative Approach
The cycle of phone number distribution starts at signup, which is why protecting the number at that initial point matters. Using a virtual phone number for service signups keeps the real number out of these systems entirely. The verification process still works, but the number that gets stored, shared, and potentially sold isn’t connected to personal communications.
This separation limits exposure to the systems described above. Marketing databases, data brokers, and third-party platforms receive a number that’s already isolated from the user’s primary contact information. If that number eventually appears in spam operations or gets breached, it doesn’t affect the personal number.
When Services Get Sold or Shut Down
Companies change ownership regularly. Startups get acquired. Apps shut down. In both cases, user data—including phone numbers—is an asset that gets transferred to new owners or sold off to recover costs.
Terms of service rarely cover what happens to data when a company stops operating. Users who signed up years ago might have their phone numbers passed to completely different organizations with different privacy standards. There’s often no notification that this transfer happened.
Acquired companies sometimes explicitly state that user data transfers with the acquisition. More often, it just happens as part of the deal. The phone number a user provided to one service ends up controlled by another service they never agreed to work with.
The Impossible Cleanup
Once a phone number enters these systems, removing it is nearly impossible. Users can delete accounts, but copies of the number often persist in backups, archived databases, and third-party systems that received it during active use. Data deletion requests might remove the number from active systems while leaving it in dozens of other locations.
This persistence is why the initial sharing decision matters so much. Once the number is out there, it stays out there in some form. Limiting where it goes in the first place is more effective than trying to claw it back later.
The Hidden Journey
Most people think providing a phone number to a service means that service has their number. The reality is that dozens or hundreds of organizations end up with it through sharing, sales, breaches, and transfers that happen without user knowledge or consent.
The signup form is just the beginning. What happens after is a journey through systems designed to extract maximum value from every piece of data collected—including those ten seemingly innocent digits.
