On the Dissection of Evasive Malware

Complex malware samples feature measures to impede automatic and manual analyses, making their investigation cumbersome. While automatic characterization of malware benefits from recently proposed designs for passive monitoring, the subsequent dissection process still sees human analysts struggling with adversarial behaviors, many of which also closely resemble those studied for automatic systems. This gap affects the day-to-day analysis of complex samples and researchers have not yet attempted to bridge it. We make a first step down this road by proposing a design that can reconcile transparency requirements with manipulation capabilities required for dissection. Our open-source prototype BluePill (i) offers a customizable execution environment that remains stealthy when analysts intervene to alter instructions and data or run third-party tools, (ii) is extensible to counteract newly encountered anti-analysis measures using insights from the dissection, and (iii) can accommodate program analyses that aid analysts, as we explore for taint analysis. On a set of highly evasive samples BluePill resulted as stealthy as commercial sandboxes while offering new intervention and customization capabilities for dissection.