An information leak is the unintended disclosure of data that should remain private or protected. The exposed data may include memory contents, file paths, addresses, usernames, tokens, or internal system details that were never meant to be visible outside a trusted boundary.
In cyber security, information leaks matter because they often reduce the attacker’s uncertainty. Even when a leak does not give direct control, it can reveal how a system is built, where sensitive values live, or which defenses are in place. Attackers use leaks to guide exploitation, bypass mitigations, or chain a weak disclosure into a larger compromise. Defenders look for signs such as debug output, verbose error messages, misconfigured access controls, and kernel or application bugs that read beyond allocated memory. Preventing leaks means limiting what software reveals, validating boundaries carefully, and treating exposed internal data as a security issue, not just a privacy problem.