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T1090.003 Multi-hop Proxy

To disguise the source of malicious traffic, adversaries may chain together multiple proxies. 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. A particular variant of this behavior is to use onion routing networks, such as the publicly available TOR network. 1

In the case of network infrastructure, particularly routers, it is possible for an adversary to leverage multiple compromised devices to create a multi-hop proxy chain within the Wide-Area Network (WAN) of the enterprise. By leveraging Patch System Image, adversaries can add custom code to the affected network devices that will implement onion routing between those nodes. This custom onion routing network will transport the encrypted C2 traffic through the compromised population, allowing adversaries to communicate with any device within the onion routing network. This method is dependent upon the Network Boundary Bridging method in order to allow the adversaries to cross the protected network boundary of the Internet perimeter and into the organization’s WAN. Protocols such as ICMP may be used as a transport.

Item Value
ID T1090.003
Sub-techniques T1090.001, T1090.002, T1090.003, T1090.004
Tactics TA0011
Platforms Linux, Network, Windows, macOS
Version 2.0
Created 14 March 2020
Last Modified 21 October 2020

Procedure Examples

ID Name Description
G0007 APT28 APT28 has routed traffic over Tor and VPN servers to obfuscate their activities.20
G0016 APT29 A backdoor used by APT29 created a Tor hidden service to forward traffic from the Tor client to local ports 3389 (RDP), 139 (Netbios), and 445 (SMB) enabling full remote access from outside the network and has also used TOR.2122
S0438 Attor Attor has used Tor for C2 communication.15
C0004 CostaRicto During CostaRicto, the threat actors used a layer of proxies to manage C2 communications.24
S0687 Cyclops Blink Cyclops Blink has used Tor nodes for C2 traffic.7
S0281 Dok Dok downloads and installs Tor via homebrew.9
S0384 Dridex Dridex can use multiple layers of proxy servers to hide terminal nodes in its infrastructure.3
G0085 FIN4 FIN4 has used Tor to log in to victims’ email accounts.17
S0342 GreyEnergy GreyEnergy has used Tor relays for Command and Control servers.11
G0100 Inception Inception used chains of compromised routers to proxy C2 communications between them and cloud service providers.19
S0604 Industroyer Industroyer used Tor nodes for C2.16
S0276 Keydnap Keydnap uses a copy of tor2web proxy for HTTPS communications.4
S0641 Kobalos Kobalos can chain together multiple compromised machines as proxies to reach their final targets.56
G0065 Leviathan Leviathan has used multi-hop proxies to disguise the source of their malicious traffic.18
S0282 MacSpy MacSpy uses Tor for command and control.9
C0014 Operation Wocao During Operation Wocao, threat actors executed commands through the installed web shell via Tor exit nodes.23
S0623 Siloscape Siloscape uses Tor to communicate with C2.12
S0491 StrongPity StrongPity can use multiple layers of proxy servers to hide terminal nodes in its infrastructure.8
S0183 Tor Traffic traversing the Tor network will be forwarded to multiple nodes before exiting the Tor network and continuing on to its intended destination.2
S0386 Ursnif Ursnif has used Tor for C2.1314
S0366 WannaCry WannaCry uses Tor for command and control traffic.10


ID Mitigation Description
M1037 Filter Network Traffic Traffic to known anonymity networks and C2 infrastructure can be blocked through the use of network allow and block lists. It should be noted that this kind of blocking may be circumvented by other techniques like Domain Fronting.


ID Data Source Data Component
DS0029 Network Traffic Network Connection Creation


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  2. Roger Dingledine, Nick Mathewson and Paul Syverson. (2004). Tor: The Second-Generation Onion Router. Retrieved December 21, 2017. 

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  13. Proofpoint Staff. (2016, August 25). Nightmare on Tor Street: Ursnif variant Dreambot adds Tor functionality. Retrieved June 5, 2019. 


  15. Dragos Inc.. (2017, June 13). CRASHOVERRIDE Analysis of the Threat to Electric Grid Operations. Retrieved December 18, 2020. 

  16. Vengerik, B. et al.. (2014, December 5). Hacking the Street? FIN4 Likely Playing the Market. Retrieved December 17, 2018. 

  17. CISA. (2021, July 19). (AA21-200A) Joint Cybersecurity Advisory – Tactics, Techniques, and Procedures of Indicted APT40 Actors Associated with China’s MSS Hainan State Security Department. Retrieved August 12, 2021. 

  18. Symantec. (2018, March 14). Inception Framework: Alive and Well, and Hiding Behind Proxies. Retrieved May 8, 2020. 

  19. Hacquebord, F., Remorin, L. (2020, December 17). Pawn Storm’s Lack of Sophistication as a Strategy. Retrieved January 13, 2021. 

  20. Dunwoody, M. and Carr, N.. (2016, September 27). No Easy Breach DerbyCon 2016. Retrieved October 4, 2016. 

  21. Microsoft Threat Intelligence Center. (2021, October 25). NOBELIUM targeting delegated administrative privileges to facilitate broader attacks. Retrieved March 25, 2022. 

  22. 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. 

  23. The BlackBerry Research and Intelligence Team. (2020, November 12). The CostaRicto Campaign: Cyber-Espionage Outsourced. Retrieved May 24, 2021.