Definition
A side-channel attack exploits information leaked from the physical implementation of a computing system rather than directly attacking software vulnerabilities. Attackers gather data like power consumption, electromagnetic radiation, or timing variations to infer sensitive information such as cryptographic keys. This method bypasses traditional security measures by observing the system's behavior during operation. For instance, an attacker might measure the power used by a smart card to deduce the secret key it is processing. Unlike direct attacks that target software flaws, side-channel attacks focus on the unintended physical emanations of hardware. This concept is crucial for understanding advanced security threats and is covered in certifications like CompTIA Security+ and CISSP.