T1648Not expressible in Sigma

Serverless Execution

ExecutionSaaS, IaaS, Office Suite

Where this stands

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

None of MITRE's analytics for this technique name a log source that maps to a Sigma logsource — they describe abstract data ("Process::None"), API-hook telemetry, or prose channels with no reliable field names behind them.

What the technique is

Adversaries may abuse serverless computing, integration, and automation services to execute arbitrary code in cloud environments. Many cloud providers offer a variety of serverless resources, including compute engines, application integration services, and web servers. Adversaries may abuse these resources in various ways as a means of executing arbitrary commands. For example, adversaries may use serverless functions to execute malicious code, such as crypto-mining malware (i.e. Resource Hijacking). Adversaries may also create functions that enable further compromise of the cloud environment. For example, an adversary may use the IAM:PassRole permission in AWS or the iam.serviceAccounts.actAs permission in Google Cloud to add Additional Cloud Roles to a serverless cloud function, which may then be able to perform actions the original user cannot. Serverless functions can also be invoked in response to cloud events (i.e. Event Triggered Execution), potentially enabling persistent execution over time. For example, in AWS environments, an adversary may create a Lambda function that automatically adds Additional Cloud Credentials to a user and a corresponding CloudWatch events rule that invokes that function whenever a new user is created. This is also possible in many cloud-based office application suites. […]

Read it on attack.mitre.org

What MITRE says you would watch

AN1053
Correlate creation or modification of serverless functions (e.g., AWS Lambda, GCP Cloud Functions, Azure Functions) with anomalous IAM role assignments or permissions escalation events. Detect subsequent executions of newly created functions that perform unexpected actions such as spawning outbound network connections, accessing sensitive resources, or creating additional credentials.
AN1054
Monitor for creation of new Power Automate flows or equivalent automation scripts that trigger on user or file events. Detect anomalous actions performed by these automations, such as email forwarding, anonymous link creation, or unexpected API calls to external endpoints.
AN1055
Track creation or update of SaaS automation scripts (e.g., Google Workspace Apps Script). Detect when these scripts are bound to user events such as file opens or account modifications, and correlate with subsequent abnormal API calls that exfiltrate or modify user data.