The charging plug can also be a data connection
A USB port carries more than electricity. Its contacts can also let a phone exchange information with the device on the other end—normally a computer, charger, or accessory. A public charging port that has been altered to act like a computer could therefore try to communicate with a connected phone, rather than simply supply power.
That creates two possible risks: the port could attempt to access data the phone makes available, or it could try to send harmful software. Neither outcome is automatic. Phones commonly restrict unfamiliar connections and may ask whether to trust a device or allow data access, but protections and prompts differ by phone and software version.
A data blocker breaks the communication path
A charge-only adapter, often called a USB data blocker, sits between the cable and the public port. It passes the electrical connection needed to charge while blocking the data contacts. With no data path, the port cannot use USB to communicate with the phone.
The tradeoff is that data-dependent features—such as transferring files or connecting to a computer—will not work through the blocker. For a public charging point, that is usually the point: keep the useful part, power, and cut the connection that is not needed.
Your own power source avoids the port
A personal power bank supplies electricity without plugging the phone into an unfamiliar public USB socket. It is a straightforward alternative when available. If using a public port, a data blocker helps turn the connection into what it was meant to be: a way to charge, not a way for another device to talk to your phone.
