Protocol Tunneling

Adversaries may tunnel network communications to and from a victim system within a separate protocol to avoid detection/network filtering and/or enable access to otherwise unreachable systems. Tunneling involves explicitly encapsulating a protocol within another. This behavior may conceal malicious traffic by blending in with existing traffic and/or provide an outer layer of encryption (similar to a VPN). Tunneling could also enable routing of network packets that would otherwise not reach their intended destination, such as SMB, RDP, or other traffic that would be filtered by network appliances or not routed over the Internet.

There are various means to encapsulate a protocol within another protocol. For example, adversaries may perform SSH tunneling (also known as SSH port forwarding), which involves forwarding arbitrary data over an encrypted SSH tunnel.[1]

Protocol Tunneling may also be abused by adversaries during Dynamic Resolution. Known as DNS over HTTPS (DoH), queries to resolve C2 infrastructure may be encapsulated within encrypted HTTPS packets.[2]

Adversaries may also leverage Protocol Tunneling in conjunction with Proxy and/or Protocol Impersonation to further conceal C2 communications and infrastructure.

ID: T1572
Sub-techniques:  No sub-techniques
Platforms: Linux, Windows, macOS
Version: 1.0
Created: 15 March 2020
Last Modified: 27 March 2020

Procedure Examples

ID Name Description
S1063 Brute Ratel C4

Brute Ratel C4 can use DNS over HTTPS for C2.[3][4]

C0027 C0027

During C0027, Scattered Spider used SSH tunneling in targeted environments.[5]

G0114 Chimera

Chimera has encapsulated Cobalt Strike's C2 protocol in DNS and HTTPS.[6]

G0080 Cobalt Group

Cobalt Group has used the Plink utility to create SSH tunnels.[7][8][9]

S0154 Cobalt Strike

Cobalt Strike uses a custom command and control protocol that is encapsulated in HTTP, HTTPS, or DNS. In addition, it conducts peer-to-peer communication over Windows named pipes encapsulated in the SMB protocol. All protocols use their standard assigned ports.[10][11]

C0004 CostaRicto

During CostaRicto, the threat actors set up remote SSH tunneling into the victim's environment from a malicious domain.[12]

S0687 Cyclops Blink

Cyclops Blink can use DNS over HTTPS (DoH) to resolve C2 nodes.[13]

S0038 Duqu

Duqu uses a custom command and control protocol that communicates over commonly used ports, and is frequently encapsulated by application layer protocols.[14]

G1016 FIN13

FIN13 has utilized web shells and Java tools for tunneling capabilities to and from compromised assets.[15]

G0037 FIN6

FIN6 used the Plink command-line utility to create SSH tunnels to C2 servers.[16]


FLIPSIDE uses RDP to tunnel traffic from a victim environment.[17]

G0117 Fox Kitten

Fox Kitten has used protocol tunneling for communication and RDP activity on compromised hosts through the use of open source tools such as ngrok and custom tool SSHMinion.[18][19][20]

S1044 FunnyDream

FunnyDream can connect to HTTP proxies via TCP to create a tunnel to C2.[21]

S1027 Heyoka Backdoor

Heyoka Backdoor can use spoofed DNS requests to create a bidirectional tunnel between a compromised host and its C2 servers.[22]

S0604 Industroyer

Industroyer attempts to perform an HTTP CONNECT via an internal proxy to establish a tunnel.[23]

S1020 Kevin

Kevin can use a custom protocol tunneled through DNS or HTTP.[24]

G0065 Leviathan

Leviathan has used protocol tunneling to further conceal C2 communications and infrastructure.[25]

G0059 Magic Hound

Magic Hound has used Plink to tunnel RDP over SSH.[26]

S1015 Milan

Milan can use a custom protocol tunneled through DNS or HTTP.[24]

S0699 Mythic

Mythic can use SOCKS proxies to tunnel traffic through another protocol.[27]

S0508 ngrok

ngrok can tunnel RDP and other services securely over internet connections.[28][29][30][31]

G0049 OilRig

OilRig has used the Plink utility and other tools to create tunnels to C2 servers.[32][33][34]

S0650 QakBot

The QakBot proxy module can encapsulate SOCKS5 protocol within its own proxy protocol.[35]

S0022 Uroburos

Uroburos has the ability to communicate over custom communications methodologies that ride over common network protocols including raw TCP and UDP sockets, HTTP, SMTP, and DNS.[36]


ID Mitigation Description
M1037 Filter Network Traffic

Consider filtering network traffic to untrusted or known bad domains and resources.

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.


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.


  1. SSH.COM. (n.d.). SSH tunnel. Retrieved March 15, 2020.
  2. Gatlan, S. (2019, July 3). New Godlua Malware Evades Traffic Monitoring via DNS over HTTPS. Retrieved March 15, 2020.
  3. Harbison, M. and Renals, P. (2022, July 5). When Pentest Tools Go Brutal: Red-Teaming Tool Being Abused by Malicious Actors. Retrieved February 1, 2023.
  4. Kenefick, I. et al. (2022, October 12). Black Basta Ransomware Gang Infiltrates Networks via QAKBOT, Brute Ratel, and Cobalt Strike. Retrieved February 6, 2023.
  5. Parisi, T. (2022, December 2). Not a SIMulation: CrowdStrike Investigations Reveal Intrusion Campaign Targeting Telco and BPO Companies. Retrieved June 30, 2023.
  6. Jansen, W . (2021, January 12). Abusing cloud services to fly under the radar. Retrieved January 19, 2021.
  7. Svajcer, V. (2018, July 31). Multiple Cobalt Personality Disorder. Retrieved September 5, 2018.
  8. Positive Technologies. (2016, December 16). Cobalt Snatch. Retrieved October 9, 2018.
  9. Matveeva, V. (2017, August 15). Secrets of Cobalt. Retrieved October 10, 2018.
  10. Strategic Cyber LLC. (2017, March 14). Cobalt Strike Manual. Retrieved May 24, 2017.
  11. Strategic Cyber LLC. (2020, November 5). Cobalt Strike: Advanced Threat Tactics for Penetration Testers. Retrieved April 13, 2021.
  12. The BlackBerry Research and Intelligence Team. (2020, November 12). The CostaRicto Campaign: Cyber-Espionage Outsourced. Retrieved May 24, 2021.
  13. Haquebord, F. et al. (2022, March 17). Cyclops Blink Sets Sights on Asus Routers. Retrieved March 17, 2022.
  14. Symantec Security Response. (2011, November). W32.Duqu: The precursor to the next Stuxnet. Retrieved September 17, 2015.
  15. Sygnia Incident Response Team. (2022, January 5). TG2003: ELEPHANT BEETLE UNCOVERING AN ORGANIZED FINANCIAL-THEFT OPERATION. Retrieved February 9, 2023.
  16. FireEye Threat Intelligence. (2016, April). Follow the Money: Dissecting the Operations of the Cyber Crime Group FIN6. Retrieved June 1, 2016.
  17. Bromiley, M. and Lewis, P. (2016, October 7). Attacking the Hospitality and Gaming Industries: Tracking an Attacker Around the World in 7 Years. Retrieved October 6, 2017.
  18. Orleans, A. (2020, August 31). Who Is PIONEER KITTEN?. Retrieved December 21, 2020.
  1. CISA. (2020, September 15). Iran-Based Threat Actor Exploits VPN Vulnerabilities. Retrieved December 21, 2020.
  2. ClearSky. (2020, December 17). Pay2Key Ransomware – A New Campaign by Fox Kitten. Retrieved December 21, 2020.
  3. Vrabie, V. (2020, November). Dissecting a Chinese APT Targeting South Eastern Asian Government Institutions. Retrieved September 19, 2022.
  4. Chen, Joey. (2022, June 9). Aoqin Dragon | Newly-Discovered Chinese-linked APT Has Been Quietly Spying On Organizations For 10 Years. Retrieved July 14, 2022.
  5. Dragos Inc.. (2017, June 13). CRASHOVERRIDE Analysis of the Threat to Electric Grid Operations. Retrieved December 18, 2020.
  6. Kayal, A. et al. (2021, October). LYCEUM REBORN: COUNTERINTELLIGENCE IN THE MIDDLE EAST. Retrieved June 14, 2022.
  7. 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.
  8. DFIR Report. (2021, November 15). Exchange Exploit Leads to Domain Wide Ransomware. Retrieved January 5, 2023.
  9. Thomas, C. (n.d.). Mythc Documentation. Retrieved March 25, 2022.
  10. Kennelly, J., Goody, K., Shilko, J. (2020, May 7). Navigating the MAZE: Tactics, Techniques and Procedures Associated With MAZE Ransomware Incidents. Retrieved May 18, 2020.
  11. Cyware. (2019, May 29). Cyber attackers leverage tunneling service to drop Lokibot onto victims’ systems. Retrieved September 15, 2020.
  12. Segura, J. (2020, February 26). Fraudsters cloak credit card skimmer with fake content delivery network, ngrok server. Retrieved September 15, 2020.
  13. Borja, A. Camba, A. et al (2020, September 14). Analysis of a Convoluted Attack Chain Involving Ngrok. Retrieved September 15, 2020.
  14. Unit42. (2016, May 1). Evasive Serpens Unit 42 Playbook Viewer. Retrieved February 6, 2023.
  15. Davis, S. and Caban, D. (2017, December 19). APT34 - New Targeted Attack in the Middle East. Retrieved December 20, 2017.
  16. Bromiley, M., et al.. (2019, July 18). Hard Pass: Declining APT34’s Invite to Join Their Professional Network. Retrieved August 26, 2019.
  17. Kuzmenko, A. et al. (2021, September 2). QakBot technical analysis. Retrieved September 27, 2021.
  18. FBI et al. (2023, May 9). Hunting Russian Intelligence “Snake” Malware. Retrieved June 8, 2023.