Replacement attacks against VM-protected applications

Process-level virtualization is increasingly being used to enhance the security of software applications from reverse engineering and unauthorized modification (called software protection). Process-level virtual machines (PVMs) can safeguard the application code at run time and hamper the adversary's ability to launch dynamic attacks on the application. This dynamic protection, combined with its flexibility, ease in handling legacy systems and low performance overhead, has made process-level virtualization a popular approach for providing software protection. While there has been much research on using process-level virtualization to provide such protection, there has been less research on attacks against PVM-protected software. In this paper, we describe an attack on applications protected using process-level virtualization, called a replacement attack. In a replacement attack, the adversary replaces the protecting PVM with an attack VM thereby rendering the application vulnerable to analysis and modification. We present a general description of the replacement attack methodology and two attack implementations against a protected application using freely available tools. The generality and simplicity of replacement attacks demonstrates that there is a strong need to develop techniques that meld applications more tightly to the protecting PVM to prevent such attacks.