ID	B0030
Objective(s)	Command and Control
Related ATT&CK Techniques	None
Version	2.1
Created	1 August 2019
Last Modified	13 September 2023

C2 Communication

All command and control malware use implant/controller communication. The methods listed below can be used to capture explicit communication details. Remote file copy behavior is captured separately, as is done in ATT&CK - see Ingress Tool Transfer (E1105).

Command and Control Communication relates to autonomous communications, not explicit, on-demand commands that malware provides to an adversary (such commands should be captured with Remote Commands under the Execution objective).

As "server" and "client" are confusing terminology, we use the terms "controller" and "implant". The controller is the software running on adversary-controlled infrastructure and used to send commands to the implant. The implant is the software running on victim-controlled infrastructure that receives commands from the adversary, executes those commands on the victim, and optionally sends the results back to the adversary.

Methods

Name	ID	Description
Authenticate	B0030.011	Implant may authenticate itself to the controller, controller may authenticate itself to implant, or both. This is often at or near the start of communication. Examples include but are not limited to a simple shared secret (e.g. password), challenge-response with symmetric encryption, or challenge-response with asymmetric encryption.
Check for Payload	B0030.005	An implant may check with the controller for additional payloads or instructions, sometimes at a regular interval. This is also known as beaconing.
Directory Listing	B0030.012	Controller requests a directory listing from the implant, optionally from a given path, optionally recursive.
Execute File	B0030.013	Execute/run/open the file using default operating system functionality, optionally with provided command-and-scripting-interpreter arguments. The file may or may not already exist on the victim.
Execute Shell Command	B0030.014	Execute/run the given command using a built-in program (e.g. cmd.exe, PowerShell, bash). This differs from Start Interactive Shell because the shell process is started only for the received command or set of commands and then exits. There is no loop looking for additional commands while the shell process is still running.
File search	B0030.015	Controller requests the implant to search for a given filename pattern, often a glob.
Implant to Controller File Transfer	B0030.004	File is transferred from implant to controller.
Receive Data	B0030.002	Receive data or command from a controller.
Request Command	B0030.008	Implant requests a command.
Request Email Address List	B0030.010	Request email address list.
Request Email Template	B0030.009	Request email template.
Send Data	B0030.001	Send data to a controller.
Send Heartbeat	B0030.007	Heartbeat sent.
Send System Information	B0030.006	Implant sends system information.
Server to Client File Transfer	B0030.003	File is transferred from controller to implant.
Start Interactive Shell	B0030.016	Starts an interactive shell using a built-in program (e.g. cmd.exe, PowerShell, bash). This is often implemented with polling the network connection from the controller for text commands to redirect to the shell's stdin and polling the shell's stdout and stderr to redirect over the network to the controller. This differs from Execute Shell Command because the shell process runs across multiple iterations of the recv-command(s)-send-result loop.

Use in Malware

Name	Date	Method	Description
CryptoWall	2014	B0030.001	The malware sends a hash value generated from system information. [1]
CryptoWall	2014	B0030.002	The malware receives a public key from the C2. [1]
CryptoLocker	2013	B0030.001	The malware sends a hash value generated from system information. [14]
CryptoLocker	2013	B0030.002	The malware receives a public key from the C2. [14]
CryptoLocker	2013	B0030.011	The malware sends a phone-home message with encryption to start. [14]
GoBotKR	2019	B0030.002	GoBotKR receives data from the C2. [2] [19]
Terminator	2013	B0030.001	The malware sends data to the C2. [3]
UP007	2016	B0030.001	The malware sends hardened HTTP headers disguised as Microsoft Update traffic. [4]
UP007	2016	B0030.002	The malware receives payloads. [4]
YiSpecter	2015	B0030.006	The malware connects to the C2 server using HTTP to send device information. [5]
Ursnif	2016	B0030.011	Ursnif variant Dreambot authenticates and encrypts traffic to the C2 server using TOR. [6]
Emotet	2018	B0030.010	New email addresses are collected automatically from the victim's address books. [7]
CHOPSTICK	2015	B0030.001	CHOPSTICK sends data to the C2 server using HTTP POST requests. [8]
CozyCar	2010	--	CozyCar communicates with a C2 server. [9]
EvilBunny	2011	--	EvilBunny communicates C2 via HTTP. [10]
Clipminer	2011	--	Clipminer communicates to a Tor Onion Service via HTTP. [11]
Matanbuchus	2021	B0030.001	The malware sends collected data about the system to C2 server. [12] [13]
Matanbuchus	2021	B0030.002	The C2 server returns Base64 encoded data containing the information about the next command for the loader. [12] [13]
Matanbuchus	2021	B0030.013	The payload is run by explorer.exe. [12] [13]
Gamut	2014	B0030.002	Gamut receives data from the C2. [15]
Gamut	2014	B0030.003	The malware receives files from the C2. [15]
GravityRAT	2018	B0030.002	GravityRAT receives data from the C2. [19]
Heriplor	2012	B0030.002	Heriplor malware has a capability to connect with a C2 to download arbitrary code. [16]
Rombertik	2015	B0030.001	The malware sends data to the C2. [17] [19]
Rombertik	2015	B0030.002	The malware receives data from the C2. [19]
Hupigon	2013	BB0030.001	The malware sends data to the C2. [19]
Hupigon	2013	B0030.002	The malware receives data from the C2. [19]
Kovter	2016	B0030.001	The malware sends data to the C2. [19]
Kovter	2016	B0030.002	The malware receives data from the C2. [19]
SearchAwesome	2018	B0030.002	The malware receives data from the C2 server. [18]
ElectroRAT	2020	--	ElectroRat communicates to a Pastebin site via HTTP. [20]

Detection

Tool: capa	Mapping	APIs
send data	C2 Communication::Send Data (B0030.001)
receive data	C2 Communication::Receive Data (B0030.002)
download and write a file	C2 Communication::Server to Client File Transfer (B0030.003)

Code Snippets

B0030.002 Snippet

C2 Communication::Receive Data

SHA256: 304f533ce9ea4a9ee5c19bc81c49838857c63469e26023f330823c3240ee4e0

asm
loc_401981
mov ecx, s
mov edx, edi
sub edx, esi
push 0 ; flags
lea eax, [esi+ebx]
push edx ;len
push eax ;buf
push ecx ;s
call recv
jmp short loc_4019A2