Adversaries may encode data 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. Use of data encoding may adhere to existing protocol specifications and includes use of ASCII, Unicode, Base64, MIME, or other binary-to-text and character encoding systems.(Citation: Wikipedia Binary-to-text Encoding) (Citation: Wikipedia Character Encoding) Some data encoding systems may also result in data compression, such as gzip.
Processes use built-in encoding utilities (e.g., `base64`, `xxd`, or `plutil`) to encode file contents followed by HTTP/HTTPS transfer via curl or custom applications.
ESXi daemons (e.g., hostd, vpxa) are wrapped or impersonated to send large outbound traffic using gzip/Base64 encoding over SSH or HTTP. These actions follow suspicious logins or shell access.
Custom scripts or processes encode outbound traffic using gzip, Base64, or hex prior to exfiltration via curl, wget, or custom sockets. Encoding typically occurs before or during outbound connections from non-network daemons.