Exfiltration Over Command and Control Channel

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Exfiltration Over Command and Control Channel
Technique
ID T1041
Tactic Exfiltration
Platform Windows Server 2003, Windows Server 2008, Windows Server 2012, Windows XP, Windows 7, Windows 8, Windows Server 2003 R2, Windows Server 2008 R2, Windows Server 2012 R2, Windows Vista, Windows 8.1, Linux, Windows 10, MacOS, OS X
Data Sources User interface, Process monitoring
Requires Network Yes

Data exfiltration is performed over the Command and Control channel. Data is encoded into the normal communications channel using the same protocol as command and control communications.

Examples

  • A Gamaredon Group file stealer transfers collected files to a hardcoded C2 server.1
  • Ke3chang transferred compressed and encrypted RAR files containing exfiltration through the established backdoor command and control channel during operations.2
  • Lazarus Group malware IndiaIndia saves information gathered about the victim to a file that is uploaded to one of its 10 C2 servers.3
  • After data is collected by Stealth Falcon malware, it is exfiltrated over the existing C2 channel.4
  • ADVSTORESHELL exfiltrates data over the same channel used for C2.5
  • Adversaries can direct BACKSPACE to upload files to the C2 Server.6
  • CallMe exfiltrates data to its C2 server over the same protocol as C2 communications.7
  • MobileOrder exfiltrates data to its C2 server over the same protocol as C2 communications.7
  • NETEAGLE is capable of reading files over the C2 channel.6
  • Psylo exfiltrates data to its C2 server over the same protocol as C2 communications.7
  • Pteranodon exfiltrates screenshot files to its C2 server.1

Mitigation

Mitigations for command and control apply. 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 obfuscation technique used by a particular adversary or tool, and will likely be different across various malware families and versions. Adversaries will likely change tool command and control signatures over time or construct protocols in such a way to avoid detection by common defensive tools.8

Detection

Detection for command and control applies. 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.8