A handheld is a portable device designed to be held and used directly in the hands. In cybersecurity, the form factor matters because handhelds are often personal, mobile, and easier to carry across trust boundaries than fixed systems. They may run a full operating system, custom firmware, or a specialized runtime, so the outside shape can hide a surprisingly complex software stack.
Handheld devices appear in attacks when adversaries steal, tamper with, or briefly access a device to extract data, install malicious profiles, or bypass controls. They also matter in defense because portability raises the value of encryption, secure boot, strong authentication, device management, and tamper-resistant storage. In practice, analysts treat a handheld like any endpoint: the small size changes the threat model, not the need for security controls. A device that looks simple may still depend on software-defined behavior, emulation, or constrained runtimes that deserve careful review.