T1481.003Not expressible in SigmaMOBILE

One-Way 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 a compromised system without receiving return output. Compromised systems may leverage popular websites and social media to host command and control (C2) instructions. Those infected systems may opt to send the output from those commands back over a different C2 channel, including to another distinct Web service. Alternatively, compromised systems may return no output at all in cases where adversaries want to send instructions to systems and do not want a response. 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

AN1663
The defender correlates repeated or periodic app-attributed retrieval from a legitimate public web-service platform with runtime conditions showing that the retrieval is not aligned to normal foreground consumption, user interaction, or approved app role. The strongest Android evidence is a managed or installed app repeatedly issuing inbound-oriented GET, fetch, sync, or content-pull operations to social, collaboration, paste, code-hosting, cloud-storage, messaging, or generic HTTPS platforms while the app is backgrounded, while the device is locked, or without recent user interaction, and without a corresponding outbound writeback to that same service class during the operational window. […]
AN1664
The defender correlates repeated retrieval-oriented communication from a supervised device or managed iOS app to a legitimate public web-service platform where the activity remains primarily inbound and does not produce corresponding writeback to that same service class during the operational window. The strongest iOS evidence is managed-app or device-attributed communication to collaboration, social, messaging, storage, or generic HTTPS platforms where inbound fetches or content pulls recur during background refresh, while the device is locked, or without recent user interaction, and no matching POST, upload, update, or message-send activity to that same public service class is observed. […]