The goal of rootkit is often to hide malicious software running on a compromised machine. While there has been significant amount of research done on different rootkits, we describe a new type of rootkit that is kernel-independent – i.e., no aspect of the kernel is modified and no code is added to the kernel address space to install the rootkit. In this work, we present PIkit – Processor-Interconnect rootkit that exploits the vulnerable hardware features within multi-socket servers that are commonly used in datacenters and high-performance computing. In particular, PIkit exploits the DRAM address mapping table structure that determines the destination node of a memory request packet in the processorinterconnect. By modifying this mapping table appropriately, PIkit enables access to victim’s memory address region without proper permission. Once PIkit is installed, only user-level code or payload is needed to carry out malicious activities. The malicious payload mostly consists of memory read and/or write instructions that appear like “normal” user-space memory accesses and it becomes very difficult to detect such malicious payload. We describe the design and implementation of PIkit on both an AMD and an Intel x86 multi-socket servers that are commonly used. We discuss different malicious activities possible with PIkit and limitations of PIkit, as well as possible software and hardware solutions to PIkit.
