Data Encoding

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Data Encoding
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

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.12 Some data encoding systems may also result in data compression, such as gzip.


  • Several BRONZE BUTLER tools encode data with base64 when posting it to a C2 server.3
  • A Lazarus Group malware sample encodes data with base64.4
  • Patchwork used Base64 to encode C2 traffic.5
  • C2 traffic from ADVSTORESHELL is encrypted, then encoded with Base64 encoding.6
  • AutoIt backdoor has sent a C2 response that was base64-encoded.7
  • BADNEWS encodes C2 traffic with base64.78
  • BS2005 uses Base64 encoding for communication in the message body of an HTTP request.9
  • CORESHELL C2 messages are Base64-encoded.10
  • Daserf uses custom base64 encoding to obfuscate HTTP traffic.3
  • Dipsind encodes C2 traffic with base64.11
  • Elise exfiltrates data using cookie values that are Base64-encoded.12
  • 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.13
  • A JHUHUGIT variant encodes C2 POST data base64.14
  • Mis-Type uses Base64 encoding for C2 traffic.15
  • Misdat network traffic is Base64-encoded plaintext.15
  • Responses from the Pisloader C2 server are base32-encoded.16
  • Prikormka encodes C2 traffic with Base64.17
  • S-Type uses Base64 encoding for C2 traffic.15
  • SeaDuke C2 traffic is base64-encoded.18


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.19


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.19