IT Forensics · Linux

Forensic analysis of the Btrfs file system – properly evaluating copy-on-write structures

Btrfs is a modern copy-on-write file system that supports subvolumes, snapshots, integrated volume management and checksumming. It is increasingly being used on desktop and Server systems, as well as in NAS solutions.

Enquire without obligation

Under the copy-on-write principle, data blocks are not overwritten directly when changes are made, but are instead rewritten, whilst old versions are retained via snapshots under certain circumstances. From a forensic perspective, this can mean both additional opportunities for reconstruction and added complexity.

Why LanCologne?

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.

Our services

We analyse Btrfs subvolumes, existing snapshots and the internal metadata structure, and check which older data states can still be reconstructed using snapshots or residual copy-on-write data.

Typical areas of application

•Analysis of Btrfs subvolumes and snapshots
•Reconstructing previous file states using snapshots
•Investigation of NAS and desktop systems using Btrfs
•Assessment of Copy-on-Write data remnants
•Incident Response on Linux Systems
•Judicial and non-judicial expert reports

This is how a Btrfs forensic analysis is carried out

Following the backup, any existing subvolumes and snapshots are first identified and documented. The internal metadata structure is then analysed to identify data remnants resulting from copy-on-write and previous states of individual files. The results are correlated with other system artefacts.

Why is Btrfs analysis relevant to forensics?

Btrfs snapshots can preserve historically valuable states of a system for forensic analysis that would no longer be available on traditional file systems. Correctly identifying and analysing them can significantly improve the reconstruction process.

At the same time, the copy-on-write principle requires a fundamentally different understanding of data overwriting than that of traditional file systems. A proper assessment therefore requires specific knowledge of Btrfs.

Frequently Asked Questions

What is copy-on-write in Btrfs?+
When changes are made, data blocks are not overwritten directly, but are written to a new location, whilst older versions may be retained via snapshots.
What forensic value do Btrfs snapshots have?+
Existing snapshots can provide additional information for reconstructing the timeline and content, provided they existed at the relevant time.
Is Btrfs widely used on the Servern?+
Btrfs is increasingly being used, including on NAS systems and certain Server and desktop distributions, but is less widespread than ext4 or XFS.

🔗 Related topics

LanCologne – Linux Forensics Cologne

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

Get in touch now