Exfiltration Over Alternative Protocol: Exfiltration Over Asymmetric Encrypted Non-C2 Protocol

Adversaries may steal data by exfiltrating it over an asymmetrically 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.

Asymmetric encryption algorithms are those that use different keys on each end of the channel. Also known as public-key cryptography, this requires pairs of cryptographic keys that can encrypt/decrypt data from the corresponding key. Each end of the communication channels requires a private key (only in the procession of that entity) and the public key of the other entity. The public keys of each entity are exchanged before encrypted communications begin.

Network protocols that use asymmetric encryption (such as HTTPS/TLS/SSL) often utilize symmetric encryption once keys are exchanged. Adversaries may opt to use these encrypted mechanisms that are baked into a protocol.

ID: T1048.002
Sub-technique of:  T1048
Tactic: Exfiltration
Platforms: Linux, Windows, macOS
Contributors: William Cain
Version: 1.1
Created: 15 March 2020
Last Modified: 15 October 2021

Procedure Examples

ID Name Description
G0007 APT28

APT28 has exfiltrated archives of collected data previously staged on a target's OWA server via HTTPS.[1]

S1040 Rclone

Rclone can exfiltrate data over SFTP or HTTPS via WebDAV.[2]

C0024 SolarWinds Compromise

During the SolarWinds Compromise, APT29 exfiltrated collected data over a simple HTTPS request to a password-protected archive staged on a victim's OWA servers.[3]


ID Mitigation Description
M1057 Data Loss Prevention

Data loss prevention can detect and block sensitive data being uploaded via web browsers.

M1037 Filter Network Traffic

Enforce proxies and use dedicated servers for services such as DNS and only allow those systems to communicate over respective ports/protocols, instead of all systems within a network.

M1031 Network Intrusion Prevention

Network intrusion detection and prevention systems that use network signatures to identify traffic for specific adversary command and control infrastructure and malware can be used to mitigate activity at the network level.

M1030 Network Segmentation

Follow best practices for network firewall configurations to allow only necessary ports and traffic to enter and exit the network.[4]


ID Data Source Data Component Detects
DS0017 Command Command Execution

Monitor executed commands and arguments that may steal data by exfiltrating it over a symmetrically encrypted network protocol other than that of the existing command and control channel.

DS0022 File File Access

Monitor files viewed in isolation that may steal data by exfiltrating it over a symmetrically encrypted network protocol other than that of the existing command and control channel.

DS0029 Network Traffic Network Connection Creation

Monitor for newly constructed network connections that are sent or received by untrusted hosts.

Network Traffic Content

Monitor and analyze traffic patterns and packet inspection associated to protocol(s) that do not follow the expected protocol standards and traffic flows (e.g extraneous packets that do not belong to established flows, gratuitous or anomalous traffic patterns, anomalous syntax, or structure). Consider correlation with process monitoring and command line to detect anomalous processes execution and command line arguments associated to traffic patterns (e.g. monitor anomalies in use of files that do not normally initiate connections for respective protocol(s)).

Network Traffic Flow

Monitor network data for uncommon data flows. Processes utilizing the network that do not normally have network communication or have never been seen before are suspicious.