Multi-Stage Channels

Adversaries may create multiple stages for command and control that are employed under different conditions or for certain functions. Use of multiple stages may obfuscate the command and control channel to make detection more difficult.

Remote access tools will call back to the first-stage command and control server for instructions. The first stage may have automated capabilities to collect basic host information, update tools, and upload additional files. A second remote access tool (RAT) could be uploaded at that point to redirect the host to the second-stage command and control server. The second stage will likely be more fully featured and allow the adversary to interact with the system through a reverse shell and additional RAT features.

The different stages will likely be hosted separately with no overlapping infrastructure. The loader may also have backup first-stage callbacks or Fallback Channels in case the original first-stage communication path is discovered and blocked.

ID: T1104
Sub-techniques:  No sub-techniques
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
G0022 APT3

An APT3 downloader first establishes a SOCKS5 connection to 192.157.198[.]103 using TCP port 1913; once the server response is verified, it then requests a connection to 192.184.60[.]229 on TCP port 81.[1]

G0096 APT41

APT41 used the storescyncsvc.dll BEACON backdoor to download a secondary backdoor.[2]

S0031 BACKSPACE

BACKSPACE attempts to avoid detection by checking a first stage command and control server to determine if it should connect to the second stage server, which performs "louder" interactions with the malware.[3]

S0534 Bazar

The Bazar loader is used to download and execute the Bazar backdoor.[4][5]

S0069 BLACKCOFFEE

BLACKCOFFEE uses Microsoft’s TechNet Web portal to obtain an encoded tag containing the IP address of a command and control server and then communicates separately with that IP address for C2. If the C2 server is discovered or shut down, the threat actors can update the encoded IP address on TechNet to maintain control of the victims’ machines.[6]

S0220 Chaos

After initial compromise, Chaos will download a second stage to establish a more permanent presence on the affected system.[7]

G0069 MuddyWater

MuddyWater has used one C2 to obtain enumeration scripts and monitor web logs, but a different C2 to send data back.[8]

S0476 Valak

Valak can download additional modules and malware capable of using separate C2 channels.[9]

Mitigations

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.

Detection

Host data that can relate unknown or suspicious process activity using a network connection is important to supplement any existing indicators of compromise based on malware command and control signatures and infrastructure. Relating subsequent actions that may result from Discovery of the system and network information or Lateral Movement to the originating process may also yield useful data.

References