An adversary may revert changes made to a cloud instance after they have performed malicious activities in attempt to evade detection and remove evidence of their presence. In highly virtualized environments, such as cloud-based infrastructure, this may be accomplished by restoring virtual machine (VM) or data storage snapshots through the cloud management dashboard or cloud APIs. Another variation of this technique is to utilize temporary storage attached to the compute instance. Most cloud providers provide various types of storage including persistent, local, and/or ephemeral, with the ephemeral types often reset upon stop/restart of the VM.(Citation: Tech Republic - Restore AWS Snapshots)(Citation: Google - Restore Cloud Snapshot)
Defenders can detect suspicious reversion of cloud compute instances by monitoring for unusual snapshot restores, rollback actions, or ephemeral storage resets that occur outside expected administrative workflows. From a defender’s perspective, relevant detection chains include: a snapshot restore triggered by a new or rarely used account, a sequence of snapshot creation immediately followed by a restore and instance start, or rollbacks performed from anomalous geographic or network locations. These patterns may indicate attempts to remove forensic evidence or re-establish a clean execution state for persistence.