Side-channel Information Leakage with CPU Frequency Scaling, but without CPU Frequency
Li Zhu, Chundong Wang · 2025
CPU frequency scaling is widely employed to dynamically adjust the speed and voltage of CPU cores in real time, aiming to achieve both high performance and power efficiency. Prior work indicates that variations in CPU frequency can leak information about the workload being processed. We find that the performance of I/O requests---such as file I/Os on a fast storage device---is affected by runtime changes in CPU frequency and, in turn, reflects the behavior of the ongoing workload. Accordingly, we develop IOLeak, a new side channel based on CPU frequency scaling that does not require direct access to the CPU frequency. We first construct an IOLeak covert channel by detecting I/O latency online for secretive communication, both in noisy and noise-free environments. Next, we leverage IOLeak to launch stealthy attacks, such as extracting cryptographic keys and fingerprinting websites, and confirm that IOLeak successfully leaks information through file I/Os.