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Data Encoding

Command and control (C2) information is encoded using a standard data encoding system. Use of data encoding may be to adhere to existing protocol specifications and includes use of ASCII, Unicode, Base64, MIME, UTF-8, or other binary-to-text and character encoding systems. [1] [2] Some data encoding systems may also result in data compression, such as gzip.

ID: T1132

Tactic: Command And Control

Platform:  Linux, macOS, Windows

Permissions Required:  User

Data Sources:  Packet capture, Process use of network, Process monitoring, Network protocol analysis

Requires Network:  Yes

Contributors:  Itzik Kotler, SafeBreach

Version: 1.0

Examples

NameDescription
ADVSTORESHELL

C2 traffic from ADVSTORESHELL is encrypted, then encoded with Base64 encoding.[3]

APT19

An APT19 HTTP malware variant used Base64 to encode communications to the C2 server.[4]

AutoIt backdoor

AutoIt backdoor has sent a C2 response that was base64-encoded.[5]

BADNEWS

BADNEWS encodes C2 traffic with base64.[5][6][7]

Bankshot

Bankshot encodes commands from the control server using a range of characters and gzip.[8]

BRONZE BUTLER

Several BRONZE BUTLER tools encode data with base64 when posting it to a C2 server.[9]

BS2005

BS2005 uses Base64 encoding for communication in the message body of an HTTP request.[10]

CORESHELL

CORESHELL C2 messages are Base64-encoded.[11]

Daserf

Daserf uses custom base64 encoding to obfuscate HTTP traffic.[9]

Dipsind

Dipsind encodes C2 traffic with base64.[12]

Elise

Elise exfiltrates data using cookie values that are Base64-encoded.[13]

Helminth

For C2 over HTTP, Helminth encodes data with base64 and sends it via the "Cookie" field of HTTP requests. For C2 over DNS, Helminth converts ASCII characters into their hexadecimal values and sends the data in cleartext.[14]

JHUHUGIT

A JHUHUGIT variant encodes C2 POST data base64.[15]

Kazuar

Kazuar encodes communications to the C2 server in Base64.[16]

Lazarus Group

A Lazarus Group malware sample encodes data with base64.[17]

Mis-Type

Mis-Type uses Base64 encoding for C2 traffic.[18]

Misdat

Misdat network traffic is Base64-encoded plaintext.[18]

OopsIE

OopsIE encodes data in hexadecimal format over the C2 channel.[19]

Patchwork

Patchwork used Base64 to encode C2 traffic.[20]

Pisloader

Responses from the Pisloader C2 server are base32-encoded.[21]

POWERSTATS

POWERSTATS encoded C2 traffic with base64.[22]

POWRUNER

POWRUNER can use base64 encoded C2 communications.[23]

Prikormka

Prikormka encodes C2 traffic with Base64.[24]

S-Type

S-Type uses Base64 encoding for C2 traffic.[18]

SeaDuke

SeaDuke C2 traffic is base64-encoded.[25]

Volgmer

Volgmer encodes files before exfiltration.[26]

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 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 C2 signatures over time or construct protocols in such a way as to avoid detection by common defensive tools. [27]

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. [27]

References

  1. Wikipedia. (2016, December 26). Binary-to-text encoding. Retrieved March 1, 2017.
  2. Wikipedia. (2017, February 19). Character Encoding. Retrieved March 1, 2017.
  3. Kaspersky Lab's Global Research and Analysis Team. (2015, December 4). Sofacy APT hits high profile targets with updated toolset. Retrieved December 10, 2015.
  4. Grunzweig, J., Lee, B. (2016, January 22). New Attacks Linked to C0d0so0 Group. Retrieved August 2, 2018.
  5. Settle, A., et al. (2016, August 8). MONSOON - Analysis Of An APT Campaign. Retrieved September 22, 2016.
  6. Levene, B. et al.. (2018, March 7). Patchwork Continues to Deliver BADNEWS to the Indian Subcontinent. Retrieved March 31, 2018.
  7. Lunghi, D., et al. (2017, December). Untangling the Patchwork Cyberespionage Group. Retrieved July 10, 2018.
  8. Sherstobitoff, R. (2018, March 08). Hidden Cobra Targets Turkish Financial Sector With New Bankshot Implant. Retrieved May 18, 2018.
  9. Counter Threat Unit Research Team. (2017, October 12). BRONZE BUTLER Targets Japanese Enterprises. Retrieved January 4, 2018.
  10. Villeneuve, N., Bennett, J. T., Moran, N., Haq, T., Scott, M., & Geers, K. (2014). OPERATION “KE3CHANG”: Targeted Attacks Against Ministries of Foreign Affairs. Retrieved November 12, 2014.
  11. FireEye. (2015). APT28: A WINDOW INTO RUSSIA’S CYBER ESPIONAGE OPERATIONS?. Retrieved August 19, 2015.
  12. Windows Defender Advanced Threat Hunting Team. (2016, April 29). PLATINUM: Targeted attacks in South and Southeast Asia. Retrieved February 15, 2018.
  13. Falcone, R., et al.. (2015, June 16). Operation Lotus Blossom. Retrieved February 15, 2016.
  14. Falcone, R. and Lee, B.. (2016, May 26). The OilRig Campaign: Attacks on Saudi Arabian Organizations Deliver Helminth Backdoor. Retrieved May 3, 2017.