Data Encoding: Standard Encoding

ID Name
T1132.001 Standard Encoding
T1132.002 Non-Standard Encoding

Adversaries may encode data with a standard data encoding system to make the content of command and control traffic more difficult to detect. Command and control (C2) information can be encoded using a standard data encoding system that adheres to existing protocol specifications. Common data encoding schemes include ASCII, Unicode, hexadecimal, Base64, and MIME.[1] [2] Some data encoding systems may also result in data compression, such as gzip.

ID: T1132.001
Sub-technique of:  T1132
Platforms: Linux, Windows, macOS
Permissions Required: User
Data Sources: Network Traffic: Network Traffic Content
Version: 1.0
Created: 14 March 2020
Last Modified: 14 March 2020

Procedure Examples

ID Name Description
S0045 ADVSTORESHELL

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

G0073 APT19

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

G0064 APT33

APT33 has used base64 to encode command and control traffic.[5]

S0373 Astaroth

Astaroth encodes data using Base64 before sending it to the C2 server. [6]

S0129 AutoIt backdoor

AutoIt backdoor has sent a C2 response that was base64-encoded.[7]

S0414 BabyShark

BabyShark has encoded data using certutil before exfiltration.[8]

S0093 Backdoor.Oldrea

Some Backdoor.Oldrea samples use standard Base64 + bzip2, and some use standard Base64 + reverse XOR + RSA-2048 to decrypt data received from C2 servers.[9]

S0128 BADNEWS

BADNEWS encodes C2 traffic with base64.[7][10][11]

S0520 BLINDINGCAN

BLINDINGCAN has encoded its C2 traffic with Base64.[12]

G0060 BRONZE BUTLER

Several BRONZE BUTLER tools encode data with base64 when posting it to a C2 server.[13]

S0014 BS2005

BS2005 uses Base64 encoding for communication in the message body of an HTTP request.[14]

S0030 Carbanak

Carbanak encodes the message body of HTTP traffic with Base64.[15][16]

S0144 ChChes

ChChes can encode C2 data with a custom technique that utilizes Base64.[17][18]

S0338 Cobian RAT

Cobian RAT obfuscates communications with the C2 server using Base64 encoding.[19]

S0137 CORESHELL

CORESHELL C2 messages are Base64-encoded.[20]

S0187 Daserf

Daserf uses custom base64 encoding to obfuscate HTTP traffic.[13]

S0354 Denis

Denis encodes the data sent to the server in Base64.[21]

S0200 Dipsind

Dipsind encodes C2 traffic with base64.[22]

S0472 down_new

down_new has the ability to base64 encode C2 communications.[23]

S0377 Ebury

Ebury has encoded C2 traffic in hexadecimal format.[24]

S0081 Elise

Elise exfiltrates data using cookie values that are Base64-encoded.[25]

S0171 Felismus

Some Felismus samples use a custom method for C2 traffic that utilizes Base64.[26]

S0410 Fysbis

Fysbis can use Base64 to encode its C2 traffic.[27]

S0032 gh0st RAT

gh0st RAT has used Zlib to compress C2 communications data before encrypting it.[28]

G0125 HAFNIUM

HAFNIUM has used ASCII encoding for C2 traffic.[29]

S0170 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.[30]

S0376 HOPLIGHT

HOPLIGHT has utilized Zlib compression to obfuscate the communications payload. [31]

S0015 Ixeshe

Ixeshe uses custom Base64 encoding schemes to obfuscate command and control traffic in the message body of HTTP requests.[32][33]

S0044 JHUHUGIT

A JHUHUGIT variant encodes C2 POST data base64.[34]

S0265 Kazuar

Kazuar encodes communications to the C2 server in Base64.[35]

S0487 Kessel

Kessel has exfiltrated data via hexadecimal-encoded subdomain fields of DNS queries.[36]

S0356 KONNI

KONNI has used a custom base64 key to encode stolen data before exfiltration.[37]

G0032 Lazarus Group

A Lazarus Group malware sample encodes data with base64.[38]

S0409 Machete

Machete has used base64 encoding.[39]

S0459 MechaFlounder

MechaFlounder has the ability to use base16 encoded strings in C2.[40]

S0084 Mis-Type

Mis-Type uses Base64 encoding for C2 traffic.[41]

S0083 Misdat

Misdat network traffic is Base64-encoded plaintext.[41]

S0284 More_eggs

More_eggs has used basE91 encoding, along with encryption, for C2 communication.[42]

G0069 MuddyWater

MuddyWater has used tools to encode C2 communications including Base64 encoding.[43][44]

S0385 njRAT

njRAT uses Base64 encoding for C2 traffic.[45]

S0340 Octopus

Octopus encodes C2 communications in Base64.[46]

S0439 Okrum

Okrum has used base64 to encode C2 communication.[47]

S0264 OopsIE

OopsIE encodes data in hexadecimal format over the C2 channel.[48]

G0040 Patchwork

Patchwork used Base64 to encode C2 traffic.[49]

S0124 Pisloader

Responses from the Pisloader C2 server are base32-encoded.[50]

S0441 PowerShower

PowerShower has the ability to encode C2 communications with base64 encoding.[51][52]

S0223 POWERSTATS

POWERSTATS encoded C2 traffic with base64.[53]

S0184 POWRUNER

POWRUNER can use base64 encoded C2 communications.[54]

S0113 Prikormka

Prikormka encodes C2 traffic with Base64.[55]

S0269 QUADAGENT

QUADAGENT encodes C2 communications with base64.[56]

S0458 Ramsay

Ramsay has used base64 to encode its C2 traffic.[57]

S0495 RDAT

RDAT can communicate with the C2 via base32-encoded subdomains.[58]

S0379 Revenge RAT

Revenge RAT uses Base64 to encode information sent to the C2 server.[59]

S0270 RogueRobin

RogueRobin base64 encodes strings that are sent to the C2 over its DNS tunnel.[60]

S0085 S-Type

S-Type uses Base64 encoding for C2 traffic.[41]

G0034 Sandworm Team

Sandworm Team's BCS-server tool uses base64 encoding and HTML tags for the communication traffic between the C2 server.[61]

S0053 SeaDuke

SeaDuke C2 traffic is base64-encoded.[62]

S0543 Spark

Spark has encoded communications with the C2 server with base64.[63]

S0374 SpeakUp

SpeakUp encodes C&C communication using Base64. [64]

S0559 SUNBURST

SUNBURST used Base64 encoding in its C2 traffic.[65]

G0127 TA551

TA551 has used encoded ASCII text for initial C2 communications.[66]

S0266 TrickBot

TrickBot can Base64-encode C2 commands.[67]

G0081 Tropic Trooper

Tropic Trooper has used base64 encoding to hide command strings delivered from the C2.[68]

S0476 Valak

Valak has returned C2 data as encoded ASCII.[66]

S0514 WellMess

WellMess has used Base64 encoding to uniquely identify communication to and from the C2.[69]

S0251 Zebrocy

Zebrocy has used URL/Percent Encoding on data exfiltrated via HTTP POST requests.[70]

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. 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.

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.[71]

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