IT Forensics · Linux

Forensic analysis of atime/mtime/ctime timestamps – Interpreting file system timestamps correctly

Linux file systems typically maintain several different timestamps for each file, including the time of the last access, the last modification of the file’s contents, and the last modification of the metadata.

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Correctly interpreting these timestamps requires a precise understanding of their respective meanings and any factors that may influence them, as even a simple read operation can inadvertently alter certain timestamps.

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 file system timestamps, taking into account their respective technical significance and any factors that may influence them, and use this information to reconstruct a reliable chronological sequence of relevant file events.

Typical areas of application

•Reconstruction of a robust file timeline
•Recording of access, modification and metadata events
•Detection of timestamp tampering
•Validation of other time-based forensic findings
•Incident Response on Linux Systems
•Judicial and non-judicial expert reports

This is how a timestamp analysis works

Following a forensically sound backup procedure, which precludes any unintentional alteration of timestamps, the relevant timestamps are systematically extracted and categorised according to their respective technical significance. Any unusual or contradictory combinations of timestamps are investigated in detail.

Why is timestamp analysis relevant in a forensic context?

A correct, technically sound interpretation of the various types of timestamps is a fundamental prerequisite for a robust forensic timeline and, at the same time, protects against misinterpretations by inadequately trained staff.

As it is possible to manipulate certain timestamps, timestamps are always checked for plausibility in the context of other, independent artefacts, rather than being considered in isolation.

Frequently Asked Questions

What exactly do atime, mtime and ctime mean?+
atime refers to the last time the file was accessed for reading, mtime to the last time the file’s content was modified, and ctime to the last time the file’s metadata was modified.
Can a simple read operation alter timestamps?+
Yes, the atime in particular can be altered simply by improper access during the investigation, which is why read-only procedures are absolutely essential.
Can tampered timestamps be detected?+
In many cases, yes – for example, by cross-referencing with independent data sources such as journaling information or backup timestamps.

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LanCologne – Linux Forensics Cologne

Do you require a professional forensic investigation into „the forensic analysis of atime/mtime/ctime timestamps"? LanCologne can assist you with the court-admissible preservation of digital evidence and the traceable analysis of relevant Linux artefacts.

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