A LNK To The Past: Utilizing LNK Files For Your Investigations

Introduction

In the vast realm of digital forensics, every byte of data can be a potential goldmine of information. Among the myriad of files and artifacts that investigators encounter, Windows “Link” or “LNK” files stand out as particularly intriguing. While many perceive these as mere shortcuts, their forensic value is immense. In this article, we’ll embark on a comprehensive exploration of LNK files, their significance in forensic investigations, and the tools that can help unlock their secrets.

What Are LNK Files?

At a glance, LNK files are shortcuts that users create for quick access to their favorite applications, documents, or games. However, beneath this simple facade lies a wealth of information. Every time a file is created or opened in Windows, the operating system automatically generates an LNK file. Depending on the Windows version, these files reside in specific directories:

• Windows 7-11: C:\Users\%username%\AppData\Roaming\Microsoft\Windows\Recent
• Windows XP: C:\Documents and Settings\%username%\Recent

Forensic Significance of LNK Files

1. File/Folder Interaction: LNK files offer a snapshot of file and folder interactions. They can reveal which files a user or a Threat Actor (TA) accessed, modified, or deleted. This becomes especially crucial when the original files are no longer available on the system.
2. Timestamps: LNK files contain multiple timestamps, including created and modified dates. These timestamps can provide a chronological record of file interactions, aiding in constructing a timeline of events.
3. Metadata: Beyond timestamps, LNK files store a plethora of metadata, such as file paths, drive letters, volume information, and even MAC timestamps. This metadata can offer insights into file origins, storage devices used, and more.

Challenges with LNK Files

LNK files, while valuable, come with their set of challenges:

1. Volatility: The ‘Recent’ folder, where LNK files are stored, has a limit. Older systems can hold up to 149 LNK files, while newer ones like Windows 10+ restrict it to 20 files per file type. This means that as new LNK files are created, older ones might be overwritten.
2. Tampering: Threat actors, aware of the forensic value of LNK files, might attempt to delete or modify them to cover their tracks.

Tools of the Trade: Eric Zimmerman’s LECmd

One of the most potent tools for parsing LNK files is Eric Zimmerman’s LECmd. This tool can delve deep into LNK files, extracting and presenting data in a comprehensible format. With LECmd, investigators can view:

• Source and target timestamps
• File paths and locations
• Volume information
• And much more

Using LECmd on a ‘Recent’ directory can yield a rich dataset, contributing to a comprehensive event timeline.

Practical Applications in Investigations

1. Tracking TA Activities: By analyzing LNK files, investigators can trace the steps of a TA, identifying which files were accessed, modified, or deleted.
2. Data Exfiltration: While proving data exfiltration can be challenging, LNK files can offer clues. By examining the LNK files of a compromised account, one can identify potential data that a TA might have accessed or copied.
3. Incident Timelines: LNK files, with their rich timestamp data, can be integrated into broader incident response timelines, providing a chronological account of events.

Conclusion

LNK files, often overlooked, are hidden treasures in the world of digital forensics. Their ability to shed light on file and folder interactions makes them invaluable in investigations. With tools like LECmd, the secrets within these files become accessible, empowering investigators to piece together digital puzzles. As technology evolves and threat actors become more sophisticated, the importance of understanding and leveraging every artifact, including LNK files, cannot be overstated.