In this paper, a novel hardware-assisted rootkit is introduced, which leverages the performance monitoring unit (PMU) of a CPU. By configuring hardware performance counters to count specific architectural events, this research effort proves it is possible to transparently trap system calls and other interrupts driven entirely by the PMU. This offers an attacker the opportunity to redirect control flow to malicious code without requiring modifications to a kernel image.
The approach is demonstrated as a kernel-mode rootkit on both the ARM and Intel x86-64 architectures that is capable of intercepting system calls while evading current kernel patch protection implementations such as PatchGuard. A proof-of-concept Android rootkit is developed targeting ARM (Krait) chipsets found in millions of smartphones worldwide, and a similar Windows rootkit is developed for the Intel x86-64 architecture. The prototype PMU-assisted rootkit adds minimal overhead to Android, and less than 10% overhead to Windows OS. Further analysis into performance counters also reveals that the PMU can be used to trap returns from secure world on ARM as well as returns from System Management Mode on x86-64.