IT Forensics · Linux

Forensic analysis of ZFS snapshots – Reconstructing previous datasets in a traceable manner

ZFS snapshots preserve a read-only state of a dataset at a specific point in time and are frequently used for backups, rollbacks or replication. They form an integral part of the ZFS architecture.

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As snapshots represent immutable references to previous data states, they can be used for forensic purposes to reconstruct files or configurations as they were at a specific point in time, even if they have already been altered in the current dataset.

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Since its foundation, LanCologne has specialised in professional IT forensics. Our staff have decades of experience in the field of information technology and assist companies, solicitors, private individuals and, on a regular basis, the courts in the technical investigation of complex digital matters.

The examination is, as a matter of principle, carried out exclusively on a forensic copy, a forensic image or a data source captured in a technically equivalent manner that preserves the integrity of the evidence. The original evidence remains unchanged and is stored in a manner that preserves its integrity.

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We identify existing ZFS snapshots, organise them chronologically and compare relevant datasets across different points in time in order to document changes in a traceable manner.

Typical areas of application

•Reconstruction of previous dataset states
•Comparing file versions across multiple snapshots
•Investigation of automated backup and replication mechanisms
•Evidence of subsequent changes to storage configurations
•Incident Response on Linux Systems
•Judicial and non-judicial expert reports

How a ZFS snapshot analysis works

Once the backup is complete, all existing ZFS snapshots are listed and sorted by time. Relevant datasets are then compared across the various snapshot points and against the current state in order to document changes accurately.

Why is ZFS snapshot analysis relevant in a forensic context?

Snapshots can preserve evidence that is no longer present in the current state of the dataset. They therefore provide an additional, often underestimated source of evidence in ZFS-based environments.

The reliability of the data depends on the specific snapshot configuration and frequency. Whether snapshots have been created, and at what intervals, must be checked on a case-by-case basis.

Frequently Asked Questions

What is a ZFS snapshot?+
A snapshot is an immutable, referenced state of a dataset at a specific point in time, which can be analysed independently of any subsequent changes.
Are ZFS snapshots created automatically?+
Not necessarily. Their presence depends on the specific system configuration and the automation tools used.
Can ZFS snapshots be deleted retrospectively?+
Yes. Whether any remaining data can still be analysed forensically depends on when it was backed up and the pool configuration.

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