3. Hidden Code Extraction

As reverse engineering becomes a prevalent technique to analyze malware, malware writers leverage various anti-reverse engineering techniques to hide their code. One technique commonly used is code packing as packed executables hinder code analysis. While this problem has been previously researched, the existing solutions are either unable to handle novel samples, or vulnerable to various evasion techniques. In this chapter, we propose a fully dynamic approach that captures an intrinsic nature of hidden code execution that the original code should be present in memory and executed at some point at run-time. Thus, this approach monitors program execution and memory writes at run-time, determines if the code under execution is newly generated, and then extracts the hidden code of the executable. To demonstrate its effectiveness, we implement a system, Renovo, and evaluate it with a large number of real-world malware samples. The experiments show that Renovo is accurate compared to previous work, yet practical in terms of performance.