IT Forensics · Linux

Forensic analysis of the ext4 file system – the basis for most Linux investigations

ext4 remains one of the most widely used Linux file systems to this day on Servern, Workstations and numerous embedded systems. It organises data using inodes, extents and a journal, which protects write operations against system crashes. From a forensic perspective, understanding this structure is an essential prerequisite for the proper examination of traditional Linux systems.

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An ext4 analysis is not limited to visible files. Inode tables, directory structures, journal entries, timestamps and metadata are all evaluated together to obtain as complete a picture as possible of system usage. In the case of encrypted or heavily fragmented systems, LUKS, LVM and the specific kernel version must also be taken into account.

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.

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We analyse inode structures, directory trees, the ext4 journal and extended attributes, and use the reconstructed activities to link them to the relevant user and system processes. The results are correlated with other Linux artefacts, such as logs and process data.

Typical areas of application

Reconstruction of file and user activities
Investigating deleted or moved files
Analysis of the ext4 journal
Assessment of fragmented or partially damaged file systems
Incident Response on Linux Systems
Judicial and non-judicial expert reports

This is how an ext4 forensic examination is carried out

Once the data carrier or its image has been securely acquired, the partition and file system structure is first determined. Inode tables, the journal and superblock information are documented and cross-referenced with the visible directory tree. Relevant file system information is then correlated with other Linux artefacts, such as logs, cron configurations and user data. All stages of the investigation are documented in a manner that allows for full traceability.

Why is the ext4 analysis so important?

On the majority of existing Linux systems, ext4 forms the technical basis for the storage of system, user and application data. An incorrect interpretation of the journal or inode structure can lead to erroneous conclusions regarding timing or content.

For this reason, ext4 artefacts are not analysed in isolation, but are always assessed in conjunction with the relevant system logs, user artefacts and application data. This is the only way to establish a forensically robust overall picture.

Frequently Asked Questions

What is ext4?+
ext4 is a widely used Linux file system and the successor to ext3; amongst other things, it supports extents, a journal and larger volume limits.
Is the original system being examined?+
No. The investigation is always carried out on a forensic copy, a forensic image or a data source that has been captured in a manner that preserves its evidential integrity.
Can deleted files on ext4 always be recovered?+
No. The options available depend, amongst other things, on the journal configuration, overwriting, SSD TRIM and the specific ext4 structure. Recovery may be severely limited or impossible.

LanCologne – Linux Forensics Cologne

Do you require a professional forensic investigation into „forensic analysis of the ext4 file system"? LanCologne can assist you with the legally admissible preservation of digital evidence and the traceable analysis of relevant Linux artefacts.

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