A memory interposer is hardware placed in the memory path, usually between a memory module and the system board, so it can observe, relay, or influence traffic. In practice, it acts like a transparent middle layer for DDR signals. Because it sits inline, it can monitor commands and data, inject delays, or modify communication under the right conditions.
In cyber security, memory interposers matter because they move an attack below the software boundary and into the physical platform. An attacker with brief physical access and the right privileges may use one to probe memory transactions, interfere with protected workloads, or test how a system responds to tampering. Defenders use similar ideas in labs for diagnostics, validation, and fault-injection research, which makes the concept useful but also risky. The key lesson is that confidential and high-assurance systems still depend on the integrity of the memory path, not just encryption or isolation inside the CPU.