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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

Procedure Examples

Name Description
ADVSTORESHELL C2 traffic from ADVSTORESHELL is encrypted, then encoded with Base64 encoding. [14]
APT19 An APT19 HTTP malware variant used Base64 to encode communications to the C2 server. [35]
APT33 APT33 has used base64 to encode command and control traffic. [38]
Astaroth Astaroth encodes data using Base64 before sending it to the C2 server. [28]
AutoIt backdoor AutoIt backdoor has sent a C2 response that was base64-encoded. [15]
BADNEWS BADNEWS encodes C2 traffic with base64. [15] [18] [19]
Bankshot Bankshot encodes commands from the control server using a range of characters and gzip. [23]
BRONZE BUTLER Several BRONZE BUTLER tools encode data with base64 when posting it to a C2 server. [25]
BS2005 BS2005 uses Base64 encoding for communication in the message body of an HTTP request. [4]
CORESHELL CORESHELL C2 messages are Base64-encoded. [20]
Daserf Daserf uses custom base64 encoding to obfuscate HTTP traffic. [25]
Denis Denis encodes the data sent to the server in Base64. [26]
Dipsind Dipsind encodes C2 traffic with base64. [9]
Ebury Ebury has encoded C2 traffic. [30]
Elise Elise exfiltrates data using cookie values that are Base64-encoded. [3]
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. [22]
JHUHUGIT A JHUHUGIT variant encodes C2 POST data base64. [16]
Kazuar Kazuar encodes communications to the C2 server in Base64. [13]
Lazarus Group A Lazarus Group malware sample encodes data with base64. [36]
Linux Rabbit Linux Rabbit sends the payload from the C2 server as an encoded URL parameter. [27]
Mis-Type Mis-Type uses Base64 encoding for C2 traffic. [6]
Misdat Misdat network traffic is Base64-encoded plaintext. [6]
njRAT njRAT uses Base64 encoding for C2 traffic. [32]
OceanSalt OceanSalt can encode data with a NOT operation before sending the data to the control server. [5]
Octopus Octopus encodes C2 communications in Base64. [17]
OopsIE OopsIE encodes data in hexadecimal format over the C2 channel. [10]
Patchwork Patchwork used Base64 to encode C2 traffic. [37]
Pisloader Responses from the Pisloader C2 server are base32-encoded. [7]
POWERSTATS POWERSTATS encoded C2 traffic with base64. [24]
POWRUNER POWRUNER can use base64 encoded C2 communications. [21]
Prikormka Prikormka encodes C2 traffic with Base64. [8]
Revenge RAT Revenge RAT uses Base64 to encode information sent to the C2 server. [31]
S-Type S-Type uses Base64 encoding for C2 traffic. [6]
SeaDuke SeaDuke C2 traffic is base64-encoded. [11]
SpeakUp SpeakUp encodes C&C communication using Base64. [29]
Ursnif Ursnif has used encoded data in HTTP URLs for C2. [33]
Volgmer Volgmer encodes files before exfiltration. [12]
Zebrocy Zebrocy has used URL/Percent Encoding on data exfiltrated via HTTP POST requests. [34]


Mitigation Description
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. 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.


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. [39]


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  1. Sardiwal, M, et al. (2017, December 7). New Targeted Attack in the Middle East by APT34, a Suspected Iranian Threat Group, Using CVE-2017-11882 Exploit. Retrieved December 20, 2017.
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  3. Sherstobitoff, R. (2018, March 08). Hidden Cobra Targets Turkish Financial Sector With New Bankshot Implant. Retrieved May 18, 2018.
  4. Lancaster, T.. (2017, November 14). Muddying the Water: Targeted Attacks in the Middle East. Retrieved March 15, 2018.
  5. Counter Threat Unit Research Team. (2017, October 12). BRONZE BUTLER Targets Japanese Enterprises. Retrieved January 4, 2018.
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