Relay Agent Reverse TCP Listener

This relay listener uses an existing agent to accept reversed connections. Instead of opening ports on the C2 system, a selected agent is configured to listen for connections. New agents connect to this relay agent, which then forwards all communication through the established channel.

Plugin ID: shelldot.listener.relay-agent-reverse-tcp

Configuration

The If omitted column describes hand-written JSON sent directly to the server. The plugin's named default example generates a random UUID and explicitly supplies host localhost, port 5555, and an empty Base64 handshake value. Replace the generated UUID with the UUID of the relay agent you intend to use.

Parameter	Type	Required	If omitted	Description
relayAgentGuid	UUID string	Yes	Invalid	UUID of the existing agent that will listen for connections.
hosts	string[]	Yes	Invalid	One or more valid hostnames or IP addresses where the relay agent can be reached.
port	int	Yes	Invalid	TCP port (1-65535) on which the relay agent will listen for connections.
handshakeBytes	Base64 string	Yes	Configuration serialization fails	Bytes used for the initial handshake between agents. Direct JSON must supply this field; use "" to disable the handshake.
startTime	string	No	null	Optional UTC start time if the listener should not start immediately.

Operation Flow

Stage	Action
Setup	Existing agent is configured to listen on specified port
Connection	New agent connects to relay agent using provided hosts
Communication	All traffic is routed through the relay agent
Security	Adds layer of indirection between new agent and C2