A USB-to-serial adapter is a bridge that lets a computer communicate with devices that speak a serial protocol such as UART, RS-232, or TTL serial. It translates data between the USB port on a modern host and the simpler serial interface used by many embedded systems, routers, industrial controllers, and lab tools.
In cyber security, USB-to-serial hardware matters because serial ports often expose low-level control outside normal network protections. Defenders use these adapters for console access, firmware updates, recovery, diagnostics, and forensic work on devices that do not offer a convenient web or SSH interface. Attackers also value them: if they can reach a serial console, they may inspect boot messages, change configuration, interrupt startup, or gain access to maintenance functions. Because of that, serial access should be treated like a privileged administrative channel, not just a cable.