Adversaries may steal data by exfiltrating it over an un-encrypted network protocol other than that of the existing command and control channel. The data may also be sent to an alternate network location from the main command and control server.(Citation: copy_cmd_cisco)

Adversaries may opt to obfuscate this data, without the use of encryption, within network protocols that are natively unencrypted (such as HTTP, FTP, or DNS). This may include custom or publicly available encoding/compression algorithms (such as base64) as well as embedding data within protocol headers and fields. 
Exfiltration Over Unencrypted Non-C2 Protocol
source_name: mitre-attack  url: https://attack.mitre.org/techniques/T1048/003  external_id: T1048.003     source_name: copy_cmd_cisco  description: Cisco. (2022, August 16). copy - Cisco IOS Configuration Fundamentals Command Reference . Retrieved July 13, 2022.  url: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/fundamentals/command/cf_command_ref/C_commands.html#wp1068167689     source_name: University of Birmingham C2  description: Gardiner, J.,  Cova, M., Nagaraja, S. (2014, February). Command & Control Understanding, Denying and Detecting. Retrieved April 20, 2016.  url: https://arxiv.org/ftp/arxiv/papers/1408/1408.1136.pdf     