An adversary may attempt to discover resources that are available within an infrastructure-as-a-service (IaaS) environment. This includes compute service resources such as instances, virtual machines, and snapshots as well as resources of other services including the storage and database services.
Cloud providers offer methods such as APIs and commands issued through CLIs to serve information about infrastructure. For example, AWS provides a DescribeInstances API within the Amazon EC2 API that can return information about one or more instances within an account, the ListBuckets API that returns a list of all buckets owned by the authenticated sender of the request, or the GetPublicAccessBlock API to retrieve access block configuration for a bucket [1][2][3]. Similarly, GCP's Cloud SDK CLI provides the gcloud compute instances list command to list all Google Compute Engine instances in a project [4], and Azure's CLI command az vm list lists details of virtual machines.[5]
An adversary may enumerate resources using a compromised user's access keys to determine which are available to that user.[6] The discovery of these available resources may help adversaries determine their next steps in the Cloud environment, such as establishing Persistence.[7]An adversary may also use this information to change the configuration to make the bucket publicly accessible, allowing data to be accessed without authentication. Adversaries have also may use infrastructure discovery APIs such as DescribeDBInstances to determine size, owner, permissions, and network ACLs of database resources. [8] Adversaries can use this information to determine the potential value of databases and discover the requirements to access them. Unlike in Cloud Service Discovery, this technique focuses on the discovery of components of the provided services rather than the services themselves.
| ID | Mitigation | Description |
|---|---|---|
| M1018 | User Account Management |
Limit permissions to discover cloud infrastructure in accordance with least privilege. Organizations should limit the number of users within the organization with an IAM role that has administrative privileges, strive to reduce all permanent privileged role assignments, and conduct periodic entitlement reviews on IAM users, roles and policies. |
Establish centralized logging for the activity of cloud infrastructure components. Monitor logs for actions that could be taken to gather information about cloud infrastructure, including the use of discovery API calls by new or unexpected users. To reduce false positives, valid change management procedures could introduce a known identifier that is logged with the change (e.g., tag or header) if supported by the cloud provider, to help distinguish valid, expected actions from malicious ones.