COMmander: Network-Based Tool for COM and RPC Exploitation

The need for solutions that improve detection skills against sophisticated attacks is growing in the ever-changing cybersecurity world.

COMmander emerges as a lightweight, C#-based utility designed to bolster defensive telemetry by monitoring Remote Procedure Call (RPC) and Component Object Model (COM) activities at a granular level.

Developed to address gaps in identifying network-based exploitations involving these protocols, COMmander taps into the Microsoft-Windows-RPC ETW provider, capturing low-level events that reveal intricate details about RPC interactions and the COM abstractions layered atop them.

This approach empowers defenders to uncover potential malicious behaviors, such as unauthorized invocations or coercion tactics, which are common in advanced persistent threats.

Network-Based Tool for COM

For an in-depth exploration of its development and associated ruleset, Jacob Acuna’s detailed blog post offers valuable insights into the tool’s inception and practical applications, highlighting how it transforms raw telemetry into actionable intelligence.

At its core, COMmander operates with remarkable simplicity and efficiency, requiring users to supply a configuration file that defines detection rules based on specific filters.

According to the Report, these rules enable precise control over monitoring, allowing for the identification of events matching criteria like InterfaceUUID, OpNum, Endpoint, NetworkAddress, or ProcessName.

For instance, a rule might target the UUID “c8cb7687-e6d3-11d2-a958-00c04f682e16” combined with the endpoint “\PIPE\DAV RPC SERVICE” to detect DCOM invocations related to WebClient, or focus on OpNum 0 within UUID “c681d488-d850-11d0-8c52-00c04fd90f7e” for spotting authentication coercion via PetitPotam EfsRpcOpenFileRaw exploits.

Operational Mechanics

Once launched, the tool continuously scans system events, alerting via terminal outputs when matches occur, all while maintaining minimal resource overhead a critical advantage given the high volume of RPC events that could otherwise overwhelm system performance.

This lightweight design ensures COMmander runs unobtrusively, making it suitable for real-time deployment in enterprise environments without significant computational burden.

Deploying COMmander is straightforward, with options for both command-line interface (CLI) execution and service-based operation.

For CLI usage, simply run COMmander.exe, which defaults to loading a config.xml file from the same directory.

Service installation involves downloading the latest release and executing InstallService.ps1 as an administrator, placing files in C:\Program Files\COMmander and running under the local system account.

Users may encounter a credentials prompt during setup, which can be dismissed by pressing enter.

Starting the service via Start-Service COMmander activates monitoring, with events logged in the Windows Event Viewer under the “COMmander” log in Application and Service Logs.

Key event IDs include 1 for service startup, 2 for shutdown, 3 for rule loading, 4 for runtime errors, and 5 for triggered detections, providing a centralized view of activities.

Uninstallation is equally simple using UninstallService.ps1. However, a key caveat is to avoid running the CLI and service simultaneously, as this can disrupt operations requiring a service restart to resolve. Building from source is effortless: open in Visual Studio and build.

While rules currently support only one instance per type, the XML-based configuration offers flexibility, as seen in sample templates that combine filters for targeted threat hunting.

Overall, COMmander’s integration of ETW-driven insights with user-defined rules positions it as an engaging, high-fidelity tool for fortifying defenses against RPC and COM exploitations, blending technical depth with operational ease to keep cybersecurity professionals one step ahead in an entertainingly complex digital arena.

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