IT Forensics · Linux

Forensic analysis of Btrfs snapshots – Reconstructing specific historical system states

Btrfs snapshots are read-only or writable references to a specific state of a subvolume at a given point in time. They are frequently used for backups, system restore points or package manager rollbacks.

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Existing snapshots can be used for forensic purposes to reconstruct files, configurations or system states as they were at an earlier point in time, even if these have already been altered or deleted in the current state.

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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 Btrfs snapshots, organise them chronologically and compare relevant files and configurations across different snapshot points in time in order to document changes in a traceable manner.

Typical areas of application

•Reconstruction of previous system states
•Comparing file versions across multiple snapshots
•Investigation of automated backup and rollback mechanisms
•Evidence of subsequent changes to configuration files
•Incident Response on Linux Systems
•Judicial and non-judicial expert reports

This is how a Btrfs snapshot analysis works

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

Why is snapshot analysis relevant in a forensic context?

Snapshots can preserve evidence that is no longer present in the current system state, for example following subsequent tampering or deletion. They therefore provide an additional, often underestimated source of evidence.

However, the reliability of the data depends heavily on the specific snapshot configuration and frequency. Not every system creates snapshots automatically, which is why their existence must be checked on a case-by-case basis.

Frequently Asked Questions

What is a Btrfs snapshot?+
A snapshot is a referenced state of a subvolume at a specific point in time, which can be analysed independently of any subsequent changes.
Are snapshots created automatically?+
Not necessarily. Whether they are present depends on the specific system configuration, for example via Snapper or package manager integrations.
Can snapshots be deleted retrospectively?+
Yes, snapshots can be deleted. Whether any remnants can still be analysed forensically depends on when the backup was taken and the extent to which the storage space has been reused.

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Do you require a professional forensic investigation into „forensic analysis of Btrfs snapshots"? LanCologne can assist you with the legally admissible preservation of digital evidence and the traceable analysis of relevant Linux artefacts.

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