Proxy: Internal Proxy

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. [1] 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.

ID: T1090.001
Sub-technique of:  T1090
Platforms: Linux, Windows, macOS
Version: 1.0
Created: 14 March 2020
Last Modified: 15 March 2020

Procedure Examples

ID Name Description
G0087 APT39

APT39 used custom tools to create SOCK5 and custom protocol proxies between infected hosts.[2][3]

S0031 BACKSPACE

The "ZJ" variant of BACKSPACE allows "ZJ link" infections with Internet access to relay traffic from "ZJ listen" to a command server.[4]

S0023 CHOPSTICK

CHOPSTICK used a proxy server between victims and the C2 server.[5]

S0154 Cobalt Strike

Cobalt Strike can be configured to have commands relayed over a peer-to-peer network of infected hosts. This can be used to limit the number of egress points, or provide access to a host without direct internet access.[6][7]

S0502 Drovorub

Drovorub can use a port forwarding rule on its agent module to relay network traffic through the client module to a remote host on the same network.[8]

S0038 Duqu

Duqu can be configured to have commands relayed over a peer-to-peer network of infected hosts if some of the hosts do not have Internet access.[9]

S0512 FatDuke

FatDuke can used pipes to connect machines with restricted internet access to remote machines via other infected hosts.[10]

G1016 FIN13

FIN13 has utilized a proxy tool to communicate between compromised assets.[11]

G0126 Higaisa

Higaisa discovered system proxy settings and used them if available.[12]

S0009 Hikit

Hikit supports peer connections.[13]

S0260 InvisiMole

InvisiMole can function as a proxy to create a server that relays communication between the client and C&C server, or between two clients.[14]

S0265 Kazuar

Kazuar has used internal nodes on the compromised network for C2 communications.[15]

G0032 Lazarus Group

Lazarus Group has used a compromised router to serve as a proxy between a victim network's corporate and restricted segments.[16]

S1060 Mafalda

Mafalda can create a named pipe to listen for and send data to a named pipe-based C2 server.[17]

S1059 metaMain

metaMain can create a named pipe to listen for and send data to a named pipe-based C2 server.[17]

S0051 MiniDuke

MiniDuke can can use a named pipe to forward communications from one compromised machine with internet access to other compromised machines.[10]

S0699 Mythic

Mythic can leverage a peer-to-peer C2 profile between agents.[18]

C0014 Operation Wocao

During Operation Wocao, threat actors proxied traffic through multiple infected systems.[19]

S0556 Pay2Key

Pay2Key has designated machines in the compromised network to serve as reverse proxy pivot points to channel communications with C2.[20][21]

C0024 SolarWinds Compromise

During the SolarWinds Compromise, APT29 used SSH port forwarding capabilities on public-facing systems, and configured at least one instance of Cobalt Strike to use a network pipe over SMB.[22][23]

G0041 Strider

Strider has used local servers with both local network and Internet access to act as internal proxy nodes to exfiltrate data from other parts of the network without direct Internet access.[24]

S0603 Stuxnet

Stuxnet installs an RPC server for P2P communications.[25]

G0010 Turla

Turla has compromised internal network systems to act as a proxy to forward traffic to C2.[26]

G1017 Volt Typhoon

Volt Typhoon has used the built-in netsh port proxy command to create proxies on compromised systems to facilitate access.[27]

S0141 Winnti for Windows

The Winnti for Windows HTTP/S C2 mode can make use of a local proxy.[28]

Mitigations

ID Mitigation Description
M1031 Network Intrusion Prevention

Network intrusion detection and prevention systems that use network signatures to identify traffic for specific adversary malware can be used to mitigate activity at the network level. Signatures are often for unique indicators within protocols and may be based on the specific C2 protocol used by a particular adversary or tool, and will likely be different across various malware families and versions. Adversaries will likely change tool C2 signatures over time or construct protocols in such a way as to avoid detection by common defensive tools.[29]

Detection

ID Data Source Data Component Detects
DS0029 Network Traffic Network Connection Creation

Monitor for newly constructed network connections that are sent or received by untrusted hosts.

Network Traffic Content

Monitor and analyze traffic patterns and packet inspection associated to protocol(s) that do not follow the expected protocol standards and traffic flows (e.g extraneous packets that do not belong to established flows, gratuitous or anomalous traffic patterns, anomalous syntax, or structure). Consider correlation with process monitoring and command line to detect anomalous processes execution and command line arguments associated to traffic patterns (e.g. monitor anomalies in use of files that do not normally initiate connections for respective protocol(s)).

Network Traffic Flow

Monitor network data for uncommon data flows. Processes utilizing the network that do not normally have network communication or have never been seen before are suspicious.

References

  1. Wilhoit, K. (2013, March 4). In-Depth Look: APT Attack Tools of the Trade. Retrieved December 2, 2015.
  2. Hawley et al. (2019, January 29). APT39: An Iranian Cyber Espionage Group Focused on Personal Information. Retrieved February 19, 2019.
  3. Rusu, B. (2020, May 21). Iranian Chafer APT Targeted Air Transportation and Government in Kuwait and Saudi Arabia. Retrieved May 22, 2020.
  4. FireEye Labs. (2015, April). APT30 AND THE MECHANICS OF A LONG-RUNNING CYBER ESPIONAGE OPERATION. Retrieved May 1, 2015.
  5. ESET. (2016, October). En Route with Sednit - Part 2: Observing the Comings and Goings. Retrieved November 21, 2016.
  6. Strategic Cyber LLC. (2017, March 14). Cobalt Strike Manual. Retrieved May 24, 2017.
  7. Strategic Cyber LLC. (2020, November 5). Cobalt Strike: Advanced Threat Tactics for Penetration Testers. Retrieved April 13, 2021.
  8. NSA/FBI. (2020, August). Russian GRU 85th GTsSS Deploys Previously Undisclosed Drovorub Malware. Retrieved August 25, 2020.
  9. Symantec Security Response. (2011, November). W32.Duqu: The precursor to the next Stuxnet. Retrieved September 17, 2015.
  10. Faou, M., Tartare, M., Dupuy, T. (2019, October). OPERATION GHOST. Retrieved September 23, 2020.
  11. Sygnia Incident Response Team. (2022, January 5). TG2003: ELEPHANT BEETLE UNCOVERING AN ORGANIZED FINANCIAL-THEFT OPERATION. Retrieved February 9, 2023.
  12. Singh, S. Singh, A. (2020, June 11). The Return on the Higaisa APT. Retrieved March 2, 2021.
  13. Novetta. (n.d.). Operation SMN: Axiom Threat Actor Group Report. Retrieved November 12, 2014.
  14. Hromcová, Z. (2018, June 07). InvisiMole: Surprisingly equipped spyware, undercover since 2013. Retrieved July 10, 2018.
  15. Accenture. (2020, October). Turla uses HyperStack, Carbon, and Kazuar to compromise government entity. Retrieved December 2, 2020.
  1. Vyacheslav Kopeytsev and Seongsu Park. (2021, February 25). Lazarus targets defense industry with ThreatNeedle. Retrieved October 27, 2021.
  2. SentinelLabs. (2022, September 22). Metador Technical Appendix. Retrieved April 4, 2023.
  3. Thomas, C. (n.d.). Mythc Documentation. Retrieved March 25, 2022.
  4. Dantzig, M. v., Schamper, E. (2019, December 19). Operation Wocao: Shining a light on one of China’s hidden hacking groups. Retrieved October 8, 2020.
  5. ClearSky. (2020, February 16). Fox Kitten – Widespread Iranian Espionage-Offensive Campaign. Retrieved December 21, 2020.
  6. Check Point. (2020, November 6). Ransomware Alert: Pay2Key. Retrieved January 4, 2021.
  7. CrowdStrike. (2022, January 27). Early Bird Catches the Wormhole: Observations from the StellarParticle Campaign. Retrieved February 7, 2022.
  8. Symantec Threat Hunter Team. (2021, January 18). Raindrop: New Malware Discovered in SolarWinds Investigation. Retrieved January 19, 2021.
  9. Kaspersky Lab's Global Research & Analysis Team. (2016, August 8). ProjectSauron: top level cyber-espionage platform covertly extracts encrypted government comms. Retrieved August 17, 2016.
  10. Nicolas Falliere, Liam O Murchu, Eric Chien 2011, February W32.Stuxnet Dossier (Version 1.4) Retrieved. 2017/09/22
  11. Cisco Talos. (2021, September 21). TinyTurla - Turla deploys new malware to keep a secret backdoor on victim machines. Retrieved December 2, 2021.
  12. Microsoft Threat Intelligence. (2023, May 24). Volt Typhoon targets US critical infrastructure with living-off-the-land techniques. Retrieved July 27, 2023.
  13. Novetta Threat Research Group. (2015, April 7). Winnti Analysis. Retrieved February 8, 2017.
  14. Gardiner, J., Cova, M., Nagaraja, S. (2014, February). Command & Control Understanding, Denying and Detecting. Retrieved April 20, 2016.