Insider Threat Investigations and Departing Employees: Where Digital Forensics Fits

When an employee leaves, the biggest question is often not what they took with them in a box. It is what they may have taken with them digitally.

The Insider Threat Challenge

Hybrid work has widened the problem. One of the biggest data security risks may not come from an outside attacker at all. It can come from inside the business, especially when someone is leaving, moving to a competitor, setting up on their own, or facing disciplinary action. These situations can quickly raise questions for legal, HR, and security teams about what information was accessed, copied, moved, or deleted.

Typical concerns include confidential documents being downloaded, company information being uploaded to personal cloud storage, files being sent to personal email accounts, data being copied to USB devices, trade secrets being retained, or evidence being deleted.

Why Digital Forensics Matters

Digital forensics helps turn scattered technical clues into a clear story. Traditional eDiscovery is often about collecting and reviewing documents. Forensic work is different: it looks at what actually happened on devices, accounts, and systems, and how a user’s activity unfolded over time. It also supports existing SIEM tools by taking alerts, log entries, and security events and checking them against endpoint and user activity evidence.

SIEM platforms are great at spotting patterns, connecting security events, and highlighting suspicious activity across the environment. A forensic investigation adds another layer by looking behind those alerts and testing what the evidence actually shows. That can include endpoint artefacts, file activity, email and cloud records, browser history, USB use, login data, and other user activity.

This helps investigators work out whether an alert points to a real issue, normal business activity, or just one part of a bigger picture. By rebuilding what happened, when it happened, and whether data was accessed, copied, transferred, or deleted, forensic analysts produce findings that are independent of the SIEM rules and detection logic. Those findings can confirm, challenge, or add context to security monitoring results, giving legal, HR, and security teams a clearer factual record to work from.

The Departing Employee Investigation

A common situation is an employee joining a competitor soon after accessing a large amount of sensitive information. Departing employees can create real risk for an organisation, especially if they still have access to confidential documents, client lists, pricing information, source code, product plans, financial data, or other intellectual property. The risk concentrates in the weeks either side of a resignation, when access is still live and intent has already changed.

These issues can lead to concerns about confidentiality breaches, misuse of trade secrets, regulatory exposure, loss of competitive advantage, and damage to client relationships. The investigation is about answering practical questions: what was accessed, what was copied or moved, what was deleted, whether the activity was normal, and whether the organisation needs to take legal, HR, security, or remediation action.

Building the Timeline

Timeline analysis brings evidence from different systems and devices together so investigators can see the order of events. In a departing employee or insider threat matter, this may mean comparing activity from laptops, mobile devices, USB connections, email accounts, cloud storage, collaboration tools, and audit logs to understand what happened and when.

By lining up file access, downloads, transfers, logins, deletions, browser activity, and communications, investigators can build a much clearer sequence of events across different devices and accounts. This joined-up view matters when activity is spread out, for example when someone accesses company data from a work laptop, syncs files through a cloud account, opens them on another device, or transfers them to removable media.

Preserving Evidence Early

Preserving evidence early matters because useful data can disappear quickly once someone leaves or an investigation starts. Devices may be reused, accounts may be switched off, logs may expire, cloud data may change, and files may be deleted either on purpose or as part of normal business processes.

Early preservation helps protect the investigation by securing key sources before they are disturbed. That can include laptops, mobile devices, email accounts, cloud storage, collaboration platforms, audit logs, and removable media records. It also helps maintain a clear chain of custody, showing when evidence was identified, collected, and handled.

By acting quickly, organisations are in a much better position to rebuild the facts, reduce the risk of missing or disputed evidence, meet legal or regulatory obligations, and make decisions based on a reliable picture of what happened.

How Lineal Can Help

Lineal helps legal, HR, and security teams respond quickly and confidently when insider threat concerns arise. Our investigations and forensics teams scope the allegation, identify the people and systems involved, preserve evidence at risk, and collect data from sources such as Microsoft 365, Teams, OneDrive, SharePoint, Slack, mobile devices, laptops, and cloud platforms. This is especially important in departing employee matters, where evidence can be lost through device reimaging, account deactivation, log expiry, or attempts to delete activity.

We have more than 50 certified forensic examiners working in region across 70+ jurisdictions, which matters when a departing employee’s data has already moved across a border before anyone noticed.

Lineal also makes sense of the evidence by building timelines, connecting user activity across systems, spotting unusual access or transfer patterns, and preparing clear reports for counsel, executives, regulators, or courts. Our approach brings together forensic preservation, chain-of-custody discipline, analytics, and eDiscovery workflows, so the findings are not only technically sound but also useful for legal strategy and business decisions.

Conclusion

Being ready for departing employee investigations before they happen makes it much easier to respond when they do. Security monitoring can flag changes in behaviour, and data loss prevention tools can detect or block some types of data exfiltration. Forensic analysis adds the extra detail by looking closely at common exfiltration routes, deletions, and anti-forensic activity, helping build a fuller picture of what the user was doing in the weeks and months before leaving the business.

If your organisation is dealing with a suspected insider threat, a departing employee concern, or an urgent preservation issue, contact Lineal to talk through how our digital forensics and eDiscovery teams can help assess the risk, preserve the evidence, and move the investigation forward.

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About Author

Laura Collins is an accomplished digital forensics examiner, currently serving as Vice President of Shared Services & Forensics at Lineal. With extensive experience overseeing global forensic operations, complex investigations, and eDiscovery delivery, she has built her career across corporate, legal, and incident‑response environments. Laura’s background spans hands‑on forensic analysis, major incident response, and leading high‑performing teams to deliver innovative, defensible solutions for clients worldwide. Recognised for her operational leadership and deep technical expertise, she is committed to advancing high‑quality forensic services while driving collaboration, efficiency, and excellence across the organisation.

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About Lineal 

Lineal is an innovative eDiscovery and legal technology solutions company that empowers law firms and corporations with modern data management and review strategies. Established in 2009, Lineal specializes in comprehensive eDiscovery services, leveraging its proprietary technology suite, Amplify™  to enhance efficiency and accuracy in handling large volumes of electronic data. With a global presence and a team of experienced professionals, Lineal is dedicated to delivering custom-tailored solutions that drive optimal legal outcomes for its clients. For more information, visit lineal.com