Digital Forensics - Investigating Cyber Incidents

About 2 min read

Digital forensics is a body of techniques for collecting, preserving, analyzing, and reporting digital evidence on computers and networks in a legally valid manner. It is used in every situation that involves digital evidence, such as investigating cybercrime, examining internal corporate fraud, and determining root causes during incident response. The word "forensic" derives from the Latin "forensis" (of the forum or court), and the decisive difference from ordinary troubleshooting is the requirement for a level of rigor that allows the evidence to be admitted in court.

The Principle of Evidence Preservation - Chain of Custody

The most important principle of digital forensics is maintaining the Chain of Custody, which proves the integrity of the evidence. From the moment evidence is collected until it is submitted to court, you must record who handled the evidence, when, and how, and prove that no tampering has occurred.

In the preservation stage, you create a complete bit-for-bit copy of the target disk (a forensic image) and record the hash value of the original (for example, SHA-256). All subsequent analysis is performed on the copy, and the original is never touched. Neglecting this procedure risks having the evidence ruled inadmissible in court.

Live Forensics vs. Dead Forensics

Modern malware increasingly takes the form of "fileless malware" that leaves no trace on disk, so the importance of live forensics grows year by year. Because evidence in memory vanishes the moment the power is cut off, acquiring a memory dump becomes the top priority as the initial response when an incident occurs.

The Importance of Memory Forensics

In memory forensics, you dump the contents of RAM and extract the following information.

The Volatility Framework is an open-source tool that has become the de facto standard for memory forensics. It supports memory dumps from Windows, Linux, and macOS, and can automate tasks such as reconstructing the process tree, extracting registry hives, and listing network connections.

Relationship to Incident Response

Forensics is conducted in earnest during the "post-containment" phase of incident response, but in practice you need to be conscious of evidence preservation from the very first response. Starting from an alert detected by a SIEM, forensic expertise shapes the quality of incident response across identifying the scope of impact, clarifying the attack path, and formulating measures to prevent recurrence. The EDR functionality of endpoint security products continuously collects the telemetry data needed for forensics, dramatically improving the efficiency of post-incident investigation.

The Challenges of Cloud Forensics

In cloud environments, there are many situations where traditional forensic methods cannot be applied as-is. Challenges include the impossibility of accessing the physical disk, the unsettled legal question of whether virtual machine snapshots are admissible as evidence, and the difficulty of isolating evidence in a multi-tenant environment. AWS and Azure provide APIs and logging services for forensics, but it is essential to clarify the boundary of responsibility with the cloud provider in advance.

A common mistake is panicking after an incident and rebooting the server, thereby losing all the evidence in memory. It is important to instill the order of "preserve the evidence first, then respond" throughout the entire organization.

Responding to data breaches is explained in detail in the article on data breach response, and incident response at the individual level is covered in the article on incident response for individuals. Please also refer to ransomware protection.digital forensics books on Amazon as well.