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.
Procedure Examples |
|
| Name | Description |
|---|---|
| JHUHUGIT |
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.(Citation: ESET Sednit Part 1) |
| Linfo |
Linfo creates a backdoor through which remote attackers can change C2 servers.(Citation: Symantec Linfo May 2012) |
| CHOPSTICK |
CHOPSTICK can switch to a new C2 channel if the current one is broken.(Citation: ESET Sednit Part 2) |
| OilRig |
OilRig malware ISMAgent falls back to its DNS tunneling mechanism if it is unable to reach the C2 server over HTTP.(Citation: OilRig ISMAgent July 2017) |
| HOPLIGHT |
HOPLIGHT has multiple C2 channels in place in case one fails.(Citation: US-CERT HOPLIGHT Apr 2019) |
| InvisiMole |
InvisiMole has been configured with several servers available for alternate C2 communications.(Citation: ESET InvisiMole June 2018)(Citation: ESET InvisiMole June 2020) |
| SslMM |
SslMM has a hard-coded primary and backup C2 string.(Citation: Baumgartner Naikon 2015) |
| 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.(Citation: ESET Ebury Oct 2017) |
| Carbanak |
Carbanak’s Harpy backdoor malware can use DNS as a backup channel for C2 if HTTP fails. (Citation: Crowdstrike GTR2020 Mar 2020) |
| BISCUIT |
BISCUIT malware contains a secondary fallback command and control server that is contacted after the primary command and control server.(Citation: Mandiant APT1)(Citation: Mandiant APT1 Appendix) |
| TrickBot |
TrickBot can use secondary C2 servers for communication after establishing connectivity and relaying victim information to primary C2 servers.(Citation: Cyberreason Anchor December 2019) |
| Valak |
Valak can communicate over multiple C2 hosts.(Citation: Unit 42 Valak July 2020) |
| S-Type |
S-Type primarily uses port 80 for C2, but falls back to ports 443 or 8080 if initial communication fails.(Citation: Cylance Dust Storm) |
| FatDuke |
FatDuke has used several C2 servers per targeted organization.(Citation: ESET Dukes October 2019) |
| QUIETEXIT |
QUIETEXIT can attempt to connect to a second hard-coded C2 if the first hard-coded C2 address fails.(Citation: Mandiant APT29 Eye Spy Email Nov 22) |
| Shark |
Shark can update its configuration to use a different C2 server.(Citation: ClearSky Siamesekitten August 2021) |
| MiniDuke |
MiniDuke uses Google Search to identify C2 servers if its primary C2 method via Twitter is not working.(Citation: Securelist MiniDuke Feb 2013) |
| WinMM |
WinMM is usually configured with primary and backup domains for C2 communications.(Citation: Baumgartner Naikon 2015) |
| Bumblebee |
Bumblebee can use backup C2 servers if the primary server fails.(Citation: Proofpoint Bumblebee April 2022) |
| Exaramel for Linux |
Exaramel for Linux can attempt to find a new C2 server if it receives an error.(Citation: ANSSI Sandworm January 2021) |
| RainyDay |
RainyDay has the ability to switch between TCP and HTTP for C2 if one method is not working.(Citation: Bitdefender Naikon April 2021) |
| Stuxnet |
Stuxnet has the ability to generate new C2 domains.(Citation: Nicolas Falliere, Liam O Murchu, Eric Chien February 2011) |
| CharmPower |
CharmPower can change its C2 channel once every 360 loops by retrieving a new domain from the actors’ S3 bucket.(Citation: Check Point APT35 CharmPower January 2022) |
| Kazuar |
Kazuar can accept multiple URLs for C2 servers.(Citation: Unit 42 Kazuar May 2017) |
| APT41 |
APT41 used the Steam community page as a fallback mechanism for C2.(Citation: FireEye APT41 Aug 2019) |
| AppleSeed |
AppleSeed can use a second channel for C2 when the primary channel is in upload mode.(Citation: Malwarebytes Kimsuky June 2021) |
|
During Night Dragon, threat actors used company extranet servers as secondary C2 servers.(Citation: McAfee Night Dragon) |
|
| Gelsemium |
Gelsemium can use multiple domains and protocols in C2.(Citation: ESET Gelsemium June 2021) |
| ShimRat |
ShimRat has used a secondary C2 location if the first was unavailable.(Citation: FOX-IT May 2016 Mofang) |
| 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.(Citation: Cylance Dust Storm) |
| Uroburos |
Uroburos can use up to 10 channels to communicate between implants.(Citation: Joint Cybersecurity Advisory AA23-129A Snake Malware May 2023) |
| NETEAGLE |
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.(Citation: FireEye APT30) |
| 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.(Citation: Novetta Blockbuster)(Citation: Novetta Blockbuster RATs) |
| SideTwist |
SideTwist has primarily used port 443 for C2 but can use port 80 as a fallback.(Citation: Check Point APT34 April 2021) |
| DustySky |
DustySky has two hard-coded domains for C2 servers; if the first does not respond, it will try the second.(Citation: DustySky) |
| TinyTurla |
TinyTurla can go through a list of C2 server IPs and will try to register with each until one responds.(Citation: Talos TinyTurla September 2021) |
| Kevin |
Kevin can assign hard-coded fallback domains for C2.(Citation: Kaspersky Lyceum October 2021) |
| Derusbi |
Derusbi uses a backup communication method with an HTTP beacon.(Citation: Fidelis Turbo) |
| Machete |
Machete has sent data over HTTP if FTP failed, and has also used a fallback server.(Citation: ESET Machete July 2019) |
| Bazar |
Bazar has the ability to use an alternative C2 server if the primary server fails.(Citation: NCC Group Team9 June 2020) |
| Crutch |
Crutch has used a hardcoded GitHub repository as a fallback channel.(Citation: ESET Crutch December 2020) |
| TAINTEDSCRIBE |
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.(Citation: CISA MAR-10288834-2.v1 TAINTEDSCRIBE MAY 2020) |
| Cardinal RAT |
Cardinal RAT can communicate over multiple C2 host and port combinations.(Citation: PaloAlto CardinalRat Apr 2017) |
| RDAT |
RDAT has used HTTP if DNS C2 communications were not functioning.(Citation: Unit42 RDAT July 2020) |
| QUADAGENT |
QUADAGENT uses multiple protocols (HTTPS, HTTP, DNS) for its C2 server as fallback channels if communication with one is unsuccessful.(Citation: Unit 42 QUADAGENT July 2018) |
| FIN7 |
FIN7's Harpy backdoor malware can use DNS as a backup channel for C2 if HTTP fails.(Citation: Crowdstrike GTR2020 Mar 2020) |
| Kwampirs |
Kwampirs uses a large list of C2 servers that it cycles through until a successful connection is established.(Citation: Symantec Orangeworm April 2018) |
| 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.(Citation: ESET Sednit Part 2) |
| PipeMon |
PipeMon can switch to an alternate C2 domain when a particular date has been reached.(Citation: ESET PipeMon May 2020) |
| Mythic |
Mythic can use a list of C2 URLs as fallback mechanisms in case one IP or domain gets blocked.(Citation: Mythc Documentation) |
| BlackEnergy |
BlackEnergy has the capability to communicate over a backup channel via plus.google.com.(Citation: Securelist BlackEnergy Nov 2014) |
| Anchor |
Anchor can use secondary C2 servers for communication after establishing connectivity and relaying victim information to primary C2 servers.(Citation: Cyberreason Anchor December 2019) |
Mitigations |
|
| Mitigation | Description |
|---|---|
| Network Intrusion Prevention |
Use intrusion detection signatures to block traffic at network boundaries. |
| Fallback Channels Mitigation |
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. (Citation: University of Birmingham C2) |
Detection
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. (Citation: University of Birmingham C2)
References
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Связанные риски
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