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. (Citation: Trend Micro APT Attack Tools) 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.
Configuration of internal NAT or proxy rules that redirect traffic between client segments internally (e.g., site-to-site port forwarding). Often used to relay internal beaconing or move traffic laterally through trust zones.
`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.
ESXi shell execution of tools/scripts (`nc`, `socat`, `perl`) relaying network traffic to other internal hosts, especially when initiated by unauthorized users or VMs.