Find sigma rule 
Attack: Data Encoding: 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.(Citation: Wikipedia Binary-to-text Encoding)(Citation: Wikipedia Character Encoding) Some data encoding systems may also result in data compression, such as gzip.
MITRE
Tactic
- command-and-control
technique
- T1132.001
Test : Base64 Encoded data (freebsd)
OS
- linux
Description:
Utilizing a common technique for posting base64 encoded data.
Executor
sh