Query: SIEM correlation: command and control activity consistent with Internal Proxy
Matching passage: T1090.001 Internal Proxy. Tactics: command and control. Description: 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](https://attack.mitre.org/software/S0040), 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.
Near-miss passage: T1090.003 Multi-hop Proxy. Tactics: command and control. Description: Adversaries may chain together multiple proxies to disguise the source of malicious traffic. Typically, a defender will be able to identify the last proxy traffic traversed before it enters their network; the defender may or may not be able to identify any previous proxies before the last-hop proxy. This technique makes identifying the original source of the malicious traffic even more difficult by requiring the defender to trace malicious traffic through several proxies to identify its source. For example, adversaries may construct or use onion routing networks – such as the publicly available [Tor](https://attack.mitre.org/software/S0183) network – to transport encrypted C2 traffic through a compromised population, allowing communication with any device within the network.(Citation: Onion Routing) Adversaries may also use operational relay box (ORB) networks composed of virtual private servers (VPS), Internet of Things (IoT) devices, smart devices, and end-of-life routers to obfuscate their operations.(Citation: ORB Mandiant) In the case of network infrastructure, it is possible for an adversary to leverage multiple compromised devices to create a multi-hop proxy chain (i.e., [Network Devices](https://attack.mitre.org/techniques/T1584/008)). By leveraging [Patch System Image](https://attack.mitre.org/techniques/T1601/001) on routers, adversaries can add custom code to the affected network devices that will implement onion routing between those nodes. This method is dependent upon the [Network Boundary Bridging](https://attack.mitre.org/techniques/T1599) method allowing the adversaries to cross the protected network boundary of the Internet perimeter and into the organization’s Wide-Area Network (WAN). Protocols such as ICMP may be used as a transport. Similarly, adversaries may abuse peer-to-peer (P2P) and blockchain-oriented infrastructure to implement routing between a decentralized network of peers.(Citation: NGLite Trojan)