Internal Proxy
Where this stands
One published detection covers this technique. Every one is unverified — no rule on Siemphony has been executed against real telemetry.
What the technique is
Adversaries may use an internal proxy to direct command and control traffic between two or more systems in a compromised environment. Many tools exist that enable traffic redirection through proxies or port redirection, including HTRAN, ZXProxy, and ZXPortMap. Adversaries use internal proxies to manage command and control communications inside a compromised environment, to reduce the number of simultaneous outbound network connections, to provide resiliency in the face of connection loss, or to ride over existing trusted communications paths between infected systems to avoid suspicion. Internal proxy connections may use common peer-to-peer (p2p) networking protocols, such as SMB, to better blend in with the environment. By using a compromised internal system as a proxy, adversaries may conceal the true destination of C2 traffic while reducing the need for numerous connections to external systems.
Read it on attack.mitre.orgWhat MITRE says you would watch
- AN0204
Anomalous process (e.g., rundll32, svchost, cmd) initiates connections to internal peer hosts not seen in typical communication baselines, used to proxy or forward traffic internally, often using SMB, RPC, or high ports.
- AN0205
socat, ssh, iptables, or ncat invoked from user space or cron jobs to create port forwarding, reverse shells, or inter-host tunnels between compromised Linux systems. Behavior is typically paired with socket activity and high entropy traffic.
- AN0206
Execution of AppleScript or Automator services launching ssh -L, socat, or launchctl items that dynamically reroute traffic from one Mac endpoint to another. LaunchAgents used to establish permanent internal tunnels.
Technique names and descriptions © MITRE ATT&CK®, CC BY 4.0. Not endorsed by MITRE.