Adversaries may use an existing, legitimate external Web service as a means for sending commands to and receiving output from a compromised system over the Web service channel. 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 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.
View in MITRE ATT&CK®| Capability ID | Capability Description | Mapping Type | ATT&CK ID | ATT&CK Name | Notes |
|---|---|---|---|---|---|
| CIS-13.10 | Perform Application Layer Filtering | mitigates | T1102.002 | Bidirectional Communication |
Comments
Application-layer filtering can block unauthorized web services used for bidirectional command-and-control communications.
References
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| CIS-13.8 | Deploy a Network Intrusion Prevention Solution | mitigates | T1102.002 | Bidirectional Communication |
Comments
Network intrusion prevention solutions can use signatures for known adversary malware to block identifiable bidirectional command-and-control traffic using web services.
References
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| CIS-4.5 | Implement and Manage a Firewall on End-User Devices | mitigates | T1102.002 | Bidirectional Communication |
Comments
Blocking unauthorized web-service destinations or preventing unapproved processes from accessing the network can disrupt bidirectional command-and-control communications.
References
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| CIS-9.3 | Maintain and Enforce Network-Based URL Filters | mitigates | T1102.002 | Bidirectional Communication |
Comments
If 9.3 implementation includes outbound web-service use broadly enough to block unauthorized services and risky websites, then this technique is applicable. ATT&CK describes two-way C2 via legitimate web services and again points to web proxies and blocking unauthorized external services as mitigation.
References
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