Digital Forensics for Beginners: Chain of Custody and First Steps

Digital forensics answers one question after something went wrong: what happened, and can we prove it? This guide covers the basic process, why evidence handling matters and how to practice safely at home.

The Basic Process

• Identify what could hold evidence: laptops, phones, servers, cloud accounts, logs.
• Preserve it so nothing changes. Power state and network connections matter.
• Acquire a copy, never working on the original.
• Analyze the copy: files, deleted data, logs, browser history, timelines.
• Report what you found, how you found it and what you could not determine.

Chain of Custody

A chain of custody is a record of who held the evidence, when and why. If a gap appears, the evidence can be challenged, and a finding that cannot be defended is of little use. Write down every transfer, date, time and person, and store evidence in a controlled place.

Never Work on the Original

Investigators take a bit-for-bit image of a disk and check it with a hash. If the hash of the copy matches the hash of the original, the copy is exact. All analysis happens on copies, so the original stays untouched. Read password cracking and hashing explained if hashes are new to you.

Practice in Your Own Lab

• Build a small lab as in our home lab guide.
• Create a Linux virtual machine and a disk image of your own test files with dd, then compare hashes with sha256sum.
• Open the image in a free tool such as Autopsy and look at the file listing and the timeline.
• Use only evidence you created or that is published for training. Never examine other people's data without permission.

Where Forensics Meets Other Work

Forensics feeds incident response and works alongside malware analysis and Windows event logs. EC-Council's CHFI certification covers the topic in 15 modules; see the CHFI exam guide.

Sources and Further Reading

• NIST SP 800-86, Guide to Integrating Forensic Techniques into Incident Response