Fallback Channels

Adversaries may use fallback or alternate communication channels if the primary channel is compromised or inaccessible in order to maintain reliable command and control and to avoid data transfer thresholds.

ID: T1008
Sub-techniques:  No sub-techniques
Tactic: Command And Control
Platforms: Linux, Windows, macOS
Data Sources: Network Traffic: Network Connection Creation, Network Traffic: Network Traffic Flow
Requires Network:  Yes
Version: 1.0
Created: 31 May 2017
Last Modified: 14 July 2020

Procedure Examples

ID Name Description
S0504 Anchor

Anchor can use secondary C2 servers for communication after establishing connectivity and relaying victim information to primary C2 servers.[1]

G0096 APT41

APT41 used the Steam community page as a fallback mechanism for C2.[2]

S0534 Bazar

Bazar has the ability to use an alternative C2 server if the primary server fails.[3]


BISCUIT malware contains a secondary fallback command and control server that is contacted after the primary command and control server.[4][5]

S0089 BlackEnergy

BlackEnergy has the capability to communicate over a backup channel via plus.google.com.[6]

G0008 Carbanak

Carbanak’s Harpy backdoor malware can use DNS as a backup channel for C2 if HTTP fails. [7]

S0348 Cardinal RAT

Cardinal RAT can communicate over multiple C2 host and port combinations.[8]


CHOPSTICK can switch to a new C2 channel if the current one is broken.[9]

S0538 Crutch

Crutch has used a hardcoded GitHub repository as a fallback channel.[10]

S0021 Derusbi

Derusbi uses a backup communication method with an HTTP beacon.[11]

S0062 DustySky

DustySky has two hard-coded domains for C2 servers; if the first does not respond, it will try the second.[12]

S0377 Ebury

Ebury has implemented a fallback mechanism to begin using a DGA when the attacker hasn't connected to the infected system for three days.[13]

S0401 Exaramel for Linux

Exaramel for Linux can attempt to find a new C2 server if it receives an error.[14]

S0512 FatDuke

FatDuke has used several C2 servers per targeted organization.[15]


HOPLIGHT has multiple C2 channels in place in case one fails.[16]

S0260 InvisiMole

InvisiMole has been configured with several servers available for alternate C2 communications.[17][18]


JHUHUGIT tests if it can reach its C2 server by first attempting a direct connection, and if it fails, obtaining proxy settings and sending the connection through a proxy, and finally injecting code into a running browser if the proxy method fails.[19]

S0265 Kazuar

Kazuar can accept multiple URLs for C2 servers.[20]

S0236 Kwampirs

Kwampirs uses a large list of C2 servers that it cycles through until a successful connection is established.[21]

G0032 Lazarus Group

Lazarus Group malware SierraAlfa sends data to one of the hard-coded C2 servers chosen at random, and if the transmission fails, chooses a new C2 server to attempt the transmission again.[22][23]

S0211 Linfo

Linfo creates a backdoor through which remote attackers can change C2 servers.[24]

S0409 Machete

Machete has sent data over HTTP if FTP failed, and has also used a fallback server.[25]

S0051 MiniDuke

MiniDuke uses Google Search to identify C2 servers if its primary C2 method via Twitter is not working.[26]

S0084 Mis-Type

Mis-Type first attempts to use a Base64-encoded network protocol over a raw TCP socket for C2, and if that method fails, falls back to a secondary HTTP-based protocol to communicate to an alternate C2 server.[27]


NETEAGLE will attempt to detect if the infected host is configured to a proxy. If so, NETEAGLE will send beacons via an HTTP POST request; otherwise it will send beacons via UDP/6000.[28]

G0049 OilRig

OilRig malware ISMAgent falls back to its DNS tunneling mechanism if it is unable to reach the C2 server over HTTP.[29]

S0501 PipeMon

PipeMon can switch to an alternate C2 domain when a particular date has been reached.[30]


QUADAGENT uses multiple protocols (HTTPS, HTTP, DNS) for its C2 server as fallback channels if communication with one is unsuccessful.[31]

S0495 RDAT

RDAT has used HTTP if DNS C2 communications were not functioning.[32]

S0085 S-Type

S-Type primarily uses port 80 for C2, but falls back to ports 443 or 8080 if initial communication fails.[27]

S0444 ShimRat

ShimRat has used a secondary C2 location if the first was unavailable.[33]

S0058 SslMM

SslMM has a hard-coded primary and backup C2 string.[34]


TAINTEDSCRIBE can randomly pick one of five hard-coded IP addresses for C2 communication; if one of the IP fails, it will wait 60 seconds and then try another IP address.[35]

S0266 TrickBot

TrickBot can use secondary C2 servers for communication after establishing connectivity and relaying victim information to primary C2 servers.[1]

S0476 Valak

Valak can communicate over multiple C2 hosts.[36]

S0059 WinMM

WinMM is usually configured with primary and backup domains for C2 communications.[34]

S0117 XTunnel

The C2 server used by XTunnel provides a port number to the victim to use as a fallback in case the connection closes on the currently used port.[9]


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 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. [37]


Analyze network data for uncommon data flows (e.g., a client sending significantly more data than it receives from a server). Processes utilizing the network that do not normally have network communication or have never been seen before are suspicious. Analyze packet contents to detect communications that do not follow the expected protocol behavior for the port that is being used. [37]


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  2. Fraser, N., et al. (2019, August 7). Double DragonAPT41, a dual espionage and cyber crime operation APT41. Retrieved September 23, 2019.
  3. Pantazopoulos, N. (2020, June 2). In-depth analysis of the new Team9 malware family. Retrieved December 1, 2020.
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  10. Faou, M. (2020, December 2). Turla Crutch: Keeping the “back door” open. Retrieved December 4, 2020.
  11. Fidelis Cybersecurity. (2016, February 29). The Turbo Campaign, Featuring Derusbi for 64-bit Linux. Retrieved March 2, 2016.
  12. ClearSky. (2016, January 7). Operation DustySky. Retrieved January 8, 2016.
  13. Vachon, F. (2017, October 30). Windigo Still not Windigone: An Ebury Update . Retrieved February 10, 2021.
  15. Faou, M., Tartare, M., Dupuy, T. (2019, October). OPERATION GHOST. Retrieved September 23, 2020.
  16. US-CERT. (2019, April 10). MAR-10135536-8 – North Korean Trojan: HOPLIGHT. Retrieved April 19, 2019.
  17. Hromcová, Z. (2018, June 07). InvisiMole: Surprisingly equipped spyware, undercover since 2013. Retrieved July 10, 2018.
  18. Hromcova, Z. and Cherpanov, A. (2020, June). INVISIMOLE: THE HIDDEN PART OF THE STORY. Retrieved July 16, 2020.
  19. ESET. (2016, October). En Route with Sednit - Part 1: Approaching the Target. Retrieved November 8, 2016.
  1. Levene, B, et al. (2017, May 03). Kazuar: Multiplatform Espionage Backdoor with API Access. Retrieved July 17, 2018.
  2. Symantec Security Response Attack Investigation Team. (2018, April 23). New Orangeworm attack group targets the healthcare sector in the U.S., Europe, and Asia. Retrieved May 8, 2018.
  3. Novetta Threat Research Group. (2016, February 24). Operation Blockbuster: Unraveling the Long Thread of the Sony Attack. Retrieved February 25, 2016.
  4. Novetta Threat Research Group. (2016, February 24). Operation Blockbuster: Remote Administration Tools & Content Staging Malware Report. Retrieved March 16, 2016.
  5. Zhou, R. (2012, May 15). Backdoor.Linfo. Retrieved February 23, 2018.
  6. ESET. (2019, July). MACHETE JUST GOT SHARPER Venezuelan government institutions under attack. Retrieved September 13, 2019.
  7. Kaspersky Lab's Global Research & Analysis Team. (2013, February 27). The MiniDuke Mystery: PDF 0-day Government Spy Assembler 0x29A Micro Backdoor. Retrieved April 5, 2017.
  8. Gross, J. (2016, February 23). Operation Dust Storm. Retrieved September 19, 2017.
  9. FireEye Labs. (2015, April). APT30 AND THE MECHANICS OF A LONG-RUNNING CYBER ESPIONAGE OPERATION. Retrieved May 1, 2015.
  10. Falcone, R. and Lee, B. (2017, July 27). OilRig Uses ISMDoor Variant; Possibly Linked to Greenbug Threat Group. Retrieved January 8, 2018.
  11. Tartare, M. et al. (2020, May 21). No “Game over” for the Winnti Group. Retrieved August 24, 2020.
  12. Lee, B., Falcone, R. (2018, July 25). OilRig Targets Technology Service Provider and Government Agency with QUADAGENT. Retrieved August 9, 2018.
  13. Falcone, R. (2020, July 22). OilRig Targets Middle Eastern Telecommunications Organization and Adds Novel C2 Channel with Steganography to Its Inventory. Retrieved July 28, 2020.
  14. Yonathan Klijnsma. (2016, May 17). Mofang: A politically motivated information stealing adversary. Retrieved May 12, 2020.
  15. Baumgartner, K., Golovkin, M.. (2015, May). The MsnMM Campaigns: The Earliest Naikon APT Campaigns. Retrieved April 10, 2019.
  16. USG. (2020, May 12). MAR-10288834-2.v1 – North Korean Trojan: TAINTEDSCRIBE. Retrieved March 5, 2021.
  17. Duncan, B. (2020, July 24). Evolution of Valak, from Its Beginnings to Mass Distribution. Retrieved August 31, 2020.
  18. Gardiner, J., Cova, M., Nagaraja, S. (2014, February). Command & Control Understanding, Denying and Detecting. Retrieved April 20, 2016.