UEC is a nickname that the ubiquitous USB (or universal serial bus) drive has acquired in recent years due to its security vulnerability. USB drives are designed to be versatile to ensure the host computer's USB port can accept a wide-range of peripheral devices, such as printers, flash drives, webcams, keyboards, cell phones etc. In order for the computer to interact with the variety of devices, USB ports negotiate an agreement or handshake which must take place between the USB controller chip built into the USB device and the hosting computer.

The fact that these controller chips on USB devices can be reprogrammed is the vulnerability. For example, a USB flash drive's controller chip can be altered to make the computer believe that it is actually a keyboard. Now all keyboard functions are given to a flash drive which may have a rogue script that either inputs or captures keystrokes. Currently there is no way for the host computer or the user to detect the presence of such malicious reprogramming.