What is chain of custody in digital forensics, and why is it critical for OT security investigations?

• A. Chain of custody documents who handled evidence, when, and how it was stored; it ensures evidence integrity, admissibility, and reproducibility
• B. Chain of custody describes the order of network devices in a topology
• C. Chain of custody is a chain of command in the incident response team
• D. Chain of custody is a legal term unrelated to OT investigations

Answer: (A)

Chain of custody is the documented, auditable trail of evidence handling—who touched the evidence, when it was handled, where it was stored, and how it was protected. This record preserves the evidence’s integrity, ensuring it remains untampered, admissible, and reproducible by others during an investigation. In OT security investigations, digital artifacts like logs, disk images, and device configurations are often used to determine what happened and when. If the chain of custody is broken, the findings can be questioned or the evidence deemed unusable, undermining the investigation and any regulatory or legal actions.

Maintaining this chain involves hashing copies to prove integrity, securing originals, restricting access, using proper imaging and write-blockers when acquiring data, and keeping time-stamped transport and storage logs. Other interpretations—such as the order of network devices, the incident response command structure, or a term unrelated to OT investigations—don’t capture the essential need to prove that evidence remains authentic and usable throughout the investigative process.