operators and automation may legitimately invoke functions from new networks (new offices, vpns, home ips, or new egress infrastructure). verify the principal in `aws.cloudtrail.user_identity.arn`, the source network, and the function, and exclude known operator networks or identities after validation.

T1648
aws
elastic

Techniques

T1648

Sample rules

AWS Lambda Function Invoked from an Unusual Source ASN

source: elastic
technicques:
- T1648

Description

Identifies an AWS Lambda function invoked directly by a principal from a source network (ASN) not seen for that principal in the prior 10 days, excluding common cloud provider networks. Direct invocation from an unfamiliar external network can indicate use of stolen execution-role or user credentials from attacker-controlled infrastructure to execute functions or retrieve the data they return. This rule relies on AWS Lambda data event logging, which is not enabled by default.

Detection logic

data_stream.dataset: "aws.cloudtrail"
    and event.provider: "lambda.amazonaws.com"
    and event.action: Invoke*
    and event.outcome: "success"
    and not aws.cloudtrail.user_identity.invoked_by: *
    and source.as.organization.name:(* and not (Amazon* or AMAZON* or Google* or GOOGLE* or Microsoft* or MICROSOFT*))