A Case Study on Investigating Insider Threats with Digital Forensics

In the highly charged world of cyber security, a breach can completely destroy a company’s reputation and viability. At SecureNet Solutions, a leading cyber security consultancy which supports the UK's critical national infrastructure, the threat was not from outside; it was the unsettling suspicion a leak from within was second-guessing their response to an insider threat. The employee at the centre of geospatial exfiltration of sensitive client files had privileged access of data the company actively transacted. The only leads available were an USB drive (issued from the company), and a number of encrypted file recovery speculations from technology surveys. This wasn't a misplaced USB key charging the reading, it settled on a considerable misconduct and breach of good faith trust understood an internally supported data exchange. To clear the cyber fog, this required robust intervention towards a planned, methodical, legally defensible digital forensic examination. 

As the assigned forensic analyst leading this examination, it was going to be my job to unpack this delicate everyday forensic situation to bring it to clear resolution. Break it down, follow the digital breadcrumbs, deduce the pathway of digital transactions then reduce everything down to an inconclusive but supportable conclusion executed to the legal and ethical obligations outlined in UK law. This is the narrative of how we went about exposing everything from initial planning to the key recommendations for SecureNet to proceed into the future.

Phase 1: The Master Plan and Legal Guardrails

Prior to commencing with data, we developed an extensive investigation plan to ensure accuracy and compliance.

Clearly Defined Mission and Scope: We then worked closely with SecureNet’s legal and IT departments to identify the investigation scope. Our focus was the suspect’s company laptop and issued USB drive in order to confirm that encrypted client files had been exfiltrated.

Preserving the Digital Crime Scene: It was essential to preserve the evidence immediately. We took possession of the devices used by the suspect and used a hardware write-blocker so the original data could not be affected. We could later process the hardware and create a forensic image of the original drive. Again, identical to preserving a physical crime scene.

Awareness of the Legal and Ethical Rights: Special attention was paid to the legal obligations and ethical rights. We made specific inquiries to ensure that our investigation was compliant with UK data protection laws, specifically the UK Data Protection Act 2018 and the UK GDPR. These regulations protect employee privacy and govern the lawful collection and processing of personal data. Every action taken was justified, transparently documented, and aligned with SecureNet’s workplace surveillance policies and legal obligations under UK legislation

Maintaining Chain of Custody: We put a proper chain of custody in place. Each turnover of evidence was explicitly documented with date, time and signature. The unbroken chain of custody will stand as the most reliable way to guarantee evidence would be admissible in court and relied upon as trustworthy evidence.

Phase 2: Forensic Imaging and Deep-Dive Analysis

Then we tackled both the technical and analytical aspects.

Forensic Imaging: Using a Tableau TD3 write-blocker and FTK Imager software, we created an exact bit-for-bit copy of the USB drive. This included calculating and validating SHA-256 and MD5 hashes for both the original device and for the image to certify the forensic integrity of the image.

Uncovering the Evidence: The forensic image identified three encrypted files titled after sensitive client projects, all of which were encrypted using AES encryption—there was an obvious intent to conceal this data. Timeline analysis indicated that these files were copied to the USB drive at 9:45 AM on the day of the incident.

Validating Device Access: A review of the registry provided direct evidence that the suspect's workstation had the USB device attached at the exact time that the files were copied to this USB drive. There was also other digital evidence, which included USB related system logs and email metadata that also connected the suspect to the USB device.

Verification and Corroboration: The verified data exfiltration through hashing checks, timeline correlation, and recovery of forensic artefacts (also including deleted and hidden files) confirmed results with high certainty.

Phase 3: Conclusion and Forward-Looking Security Enhancements

The evidence was very clear: the employee knowingly went outside company policy by leaking information and tried to cover it up by using encryption.

Our final report had very clear findings and effectively made an insider data theft verdict. We recommended ways to enhance SecureNet's controls and security, such as:

Adoption and enforcement of Data Loss Prevention (DLP) systems - Automated barriers against unintentional outbound data leaks (removable media and external networks/encrypted USB drives).

Adoption and enforcement of strict access control measures - Least privilege access, which means limiting what data is available unnecessarily.

Monitoring and auditing - Constant behavioral analysis and alerts to alert yesterday's suspicious data activity.

Security awareness training - Make employees aware of the legal implications of being the cause of data breaches and recognize threats to insider risks to report and protect data.

The investigation had shown one of the biggest potential vulnerabilities in so many organizations: trusted insiders with unrestricted access to utilize data. However, through detailed forensic processes, legal documentation, and a robust and proactive approach to enhancing security policies, SecureNet Solutions can now make this incident a foundation for a more student, better defended method of protecting sensitive, valuable information going forward. 

While this case may have been an incident, it serves as a powerful reminder: the way to digital security begins by investigating the world beneath the cover of surface, determine truth, and erect safe barriers where previously cracks were evident.