ShadowForge C2 is an API-centric Proof of Concept, similar to other C2s. The implant works with HTTP/v2 and TLS connecting over Zoom. The approach taken by this C2 is built upon an implementation strategy that leverages the capabilities of the Zoom Messaging Channel. The implant, residing within the compromised systems, establishes a connection to a designated Zoom Messaging Channel, serving as a secure and discreet communication medium. The domain used has a valid certificate, api.zoom.us.

ShadowForge is not a complete C2, and its purpose is to serve a basic understanding for beginners of how this communication works from a team server to the compromised implant. The short purpose is to learn the methodology and steps used during the communication. The C2 doesn't provide any advanced obfuscation, i.e., it's not a ready-to-use C2; This aims to provide a short introduction to using a different secure communication. To Summarize, the project is intended for other red teamers and security researchers to learn.

There's the Quickstart Guide to setting up the Zoom API.

• Implant

  • A C++-compiled implant, when executed, sends the very first call back to a Zoom Chat Channel, hardcoded in the executable.
  • Every 10 seconds, the implant checks for any updated command to execute; if the command is in this format command: <COMMAND>, the implant executes the command.
  • Once the implant executes the commands, it updates the message with result: <OUTPUT>.
  • The communication is done over TLS with HTTP/2, used library is wininet.h
  • There are quite a few downsides and limitations so far; the most important ones are that the API token used to Send/Receive messages lasts 60 mins from the time generated.

• Team Server

  • Every 12 seconds, a thread on the team server checks if the message is updated with the result; if this message is updated, it just prints the output.
  • The shell commands are received base64 encoded, as the Zoom Message's format is terrible. The team server decodes and prints correctly.
  • Keeping this in mind, the Zoom Channels are being Man-In-The-Middle for the Command & Control Communication.
  • The Implant and Team server is not connected directly; that's been said, the probability of crashing the implant is significantly less.

• Fix the Zoom API Message Length Limit
  • Base64 encode the command's output, Split the b64 encoded output, and send the output, as reply to the parent message.
• Upload/Download Feature
• Some basic Evasion
• Dynamic Sleep Timers
• Self Distruct Channels