A binary digit, or bit, is the smallest unit of digital information. It can hold one of two values: 0 or 1. Computers use bits to represent everything from numbers and text to instructions, memory state, and network traffic. Groups of bits form bytes, registers, packets, and file contents.
In cyber security, bits matter because attacks often work by changing them. A single flipped bit can corrupt data, alter a program, weaken a signature check, or change a permission flag. Defenders also rely on bits when they validate hashes, compare access tokens, encrypt data, and monitor memory for tampering. Understanding how a system stores and moves bits helps analysts spot bugs, detect manipulation, and reason about whether a device’s state is trustworthy.