Description

The Sliver Command & Control (C2) framework, an open-source Go-based tool, has gained popularity among offensive security professionals because of its flexibility and simplicity. Nevertheless, as Endpoint Detection and Response (EDR) solutions mature, conventional Sliver payloads are more and more detected by these systems, mainly because of their large binary size and recognizable static signatures included in its protocol files. New research shows how small, strategic changes to the framework's source code can profoundly improve its capabilities to avoid being detected, holding great value for red team operators. One of the most common issues with the default configuration of Sliver is its high binary size (of up to 30 MB) that makes it vulnerable to being detected through YARA rules pointing to static signatures. By altering static components like renaming certain strings within the sliver.proto file, scientists were able to effectively weaken these detection mechanisms considerably. Further, behavioral detections like Sliver's dependency on the AMSI bypass through Donut were also detected by contemporary EDR systems. In response, the authors of Sliver customized the generation process of the shellcode as well as innovating memory-mapping mechanisms so as to bypass triggering runtime alarms and therefore maximize its evasion efficiency. Customization's third step aimed to circumvent detection through more sophisticated runtime-based methods. For example, Sliver's utilization of Go's LazyDLL type triggered warnings for "Network Library Loaded from Unbacked Memory." To counter this, the researchers utilized techniques such as module stomping and API hooking, but instead settled on more straightforward solutions such as writing dynamic libraries to disk with altered export functions. Upon applying these modifications, the tailored Sliver payloads were tested against various EDR solutions with no detections in static scans and evading runtime alerts in sandbox environments successfully. This study points to the ongoing development of offensive security tools and the never-ending arms race with defensive technologies, highlighting the necessity for both sides to innovate based on the other's developments.