Web Service: Bidirectional Communication

Adversaries may use an existing, legitimate external Web service channel as a means for sending commands to and receiving output from a compromised system. Compromised systems may leverage popular websites and social media to host command and control (C2) instructions. Those infected systems can then send the output from those commands back over that Web service channel. The return traffic may occur in a variety of ways, depending on the Web service being utilized. For example, the return traffic may take the form of the compromised system posting a comment on a forum, issuing a pull request to development project, updating a document hosted on a Web service, or by sending a Tweet.

Popular websites and social media, acting as a mechanism for C2, may give a significant amount of cover. This is due to the likelihood that hosts within a network are already communicating with them prior to a compromise. Using common services, such as those offered by Google or Twitter, makes it easier for adversaries to hide in expected noise. Web service providers commonly use SSL/TLS encryption, giving adversaries an added level of protection.

ID: T1481.002
Sub-technique of:  T1481
Tactic Type: Post-Adversary Device Access
Platforms: Android, iOS
Version: 1.2
Created: 06 April 2022
Last Modified: 14 August 2023

Procedure Examples

ID Name Description
S0655 BusyGasper

BusyGasper can be controlled via IRC using freenode.net servers.[1]

S0485 Mandrake

Mandrake has used Firebase for C2.[2]

S0545 TERRACOTTA

TERRACOTTA has used Firebase for C2 communication.[3]

Mitigations

This type of attack technique cannot be easily mitigated with preventive controls since it is based on the abuse of system features.

Detection

ID Data Source Data Component Detects
DS0041 Application Vetting Network Communication

Application vetting services may provide a list of connections made or received by an application, or a list of domains contacted by the application.

DS0029 Network Traffic Network Connection Creation

Many properly configured firewalls may naturally block bidirectional command and control traffic.

References