An interposer is a hardware layer placed between two components so it can influence how they connect, signal, or exchange data. In systems engineering, it may be used for debugging, measurement, or adapting incompatible interfaces. In security research, the same idea can be used to alter traffic, delay communication, or observe what one component sends to another.
Interposers matter in cyber security because they operate below software and can affect the physical trust path between devices. That makes them relevant to attacks on memory buses, storage links, and other high-value channels where confidentiality and integrity depend on honest hardware behavior. Defenders use the term when discussing tamper-resistant design, platform validation, and controls that assume an attacker may have brief physical access. A well-placed interposer can expose hidden assumptions in secure systems by changing what a processor or controller sees on the wire.