T1481.002Not expressible in SigmaMOBILE

Bidirectional Communication

Command and ControlAndroid, iOS

Where this stands

No Sigma rule can address this — the telemetry MITRE names has no Sigma logsource behind it.

Sigma has no logsource taxonomy for mobile platforms. MITRE's telemetry here is mobile EDR and device APIs, which no Sigma rule can address.

What the technique is

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.

Read it on attack.mitre.org

What MITRE says you would watch

AN1816
The defender correlates repeated inbound retrieval and outbound submission activity by the same Android app identity to the same legitimate public web-service class within a short operational window, where the two-way exchange is inconsistent with the app's approved role, interaction model, or background behavior baseline. The strongest Android evidence is app-attributed communication to collaboration, social, cloud storage, code-hosting, messaging, or generic HTTPS platforms where requests that retrieve content are followed by app-attributed posts, uploads, document updates, API writes, or repeated small bidirectional exchanges, especially when they occur while the app is backgrounded, whil […]
AN1817
The defender correlates repeated retrieval and outbound submission activity from a supervised device or managed iOS app to the same legitimate public web-service class where the two-way exchange does not fit the bundle's approved role or expected background-refresh model. The strongest iOS evidence is managed-app or device-attributed communication to collaboration, storage, messaging, social, or generic HTTPS platforms where inbound content fetches are followed by outbound writes, uploads, updates, or message submissions within a short window, especially when occurring during background refresh, while the device is locked, or without recent user interaction. […]