In the aftermath of a security or supply chain incident, piecing together what occurred, who was involved, who was affected, and how to prevent a similar attack from taking place again, is one of the biggest challenges facing enterprise security leaders.

Metadata (the descriptive text that lies within digital data) proves to be a powerful ally in digital forensics investigations. While this data is generally not visible when viewing or interacting with a file’s content, it can also be exploited in its own right, so security leaders and decision-makers must remain vigilant about its accessibility and vulnerability.

The Dual Nature of Organizational Metadata

Metadata comprises information that’s embedded within files, and the types of data can range from email headers, timestamps, IP addresses and embedded documents, or application properties to a file’s last modified dates, user permissions, attributes, size, and location of origin.

This hidden and concealable information provides a proverbial digital footprint of a file, providing valuable contextual information about digital data. Metadata can be used to prove and disprove a file’s authenticity, statements, and understand user activity or a timeline of events. Primarily, however, it can be used to connect different pieces of evidence together, and help security departments locate and extract relevant data to uphold security hygiene.

That said, there are some exposure risks if metadata is not properly managed. The same attributes that help investigators reconstruct timelines and verify authenticity can inadvertently leak sensitive organizational intelligence to threat actors when documents are shared externally, perhaps to vendors or proprietary third-party systems that may be inadvertently compromised, unbeknownst to the user.

Common Types of Metadata Used in Forensic Investigations

File System Metadata

Operating systems (OS) maintain extensive metadata across an organization’s entire underlying architecture. For example, Windows NTFS stores information in Master File Table entries, while Linux Extended File System versions preserve data in Inodes and Directory Entries and Apple's File System uses containers and volumes for metadata storage. Internal security teams can locate and isolate system-level metadata to establish when files were created, accessed, modified, or deleted, allowing them to build an accurate, logical incident timeline.

Application Metadata

Microsoft Office applications, such as Word, PowerPoint, Excel and so on, embed properties within documents that track data and information about the document itself. This can include ownership, access control, revision history, and originating IP addresses. This may also extend to email providers, with email headers often containing vital routing information, such as timestamps, clients, message IDs, IP addresses, and email server or client information. 

The metadata generated by these applications proves vital when understanding legal requirements and metadata disclosure procedures should an investigation be launched. For example, legal experts Hassans succinctly summarize the key points arising from a recent judgment: “metadata should be provided with disclosed documents…[and] if redactions are not properly applied the party disclosing those documents may be forced to disclose all of its redacted documents.”

Mobile Device Metadata

Smartphones autonomously generate rich metadata streams through built-in applications for messaging, camera, location, and others. Internal or external security investigations often require the disclosure of mobile metadata to allow investigators to understand user behavior, verify statements, and connect otherwise disparate pieces of digital evidence to form an understanding of the events. Message metadata, for example, can unveil conversations between participants, timestamps, read status, and other important digitized patterns of events.

Using Metadata in Digital Forensics 

While organizational structures vary from one architecture to the next, metadata can be leveraged and extracted in the following methods.

• It can establish a sequence of events with precise mapping; access timestamps unveil unusual activity patterns.

• In disputes involving document tampering, metadata provides verifiable and irrefutable proof by allowing investigators to examine underlying data for alteration traces.

• File path metadata, for example, can expose relationships between documents and shared network locations.

• Email metadata can allow investigators to validate communication channels between recipients and senders, as well as confirm compliance with relevant security protocols.

• Application metadata can reveal program usage, installation, dates and permission changes, helping establish if employees used unauthorized software, failed to patch vulnerabilities, or concealed content before data transfer.

The Metadata Exposure Problem

While metadata provides integral investigative evidence, organizations routinely unveil it externally without meaning to. For instance, documents posted to websites often retain their embedded metadata containing usernames, file server paths, software versions, and device names, which could be valuable to an external threat actor in preparation for an attack.

Metadata can be extracted from publicly available documents to map organizational infrastructure. File paths that expose top-level folders can reveal a broader network topology and sensitive project or intellectual property information.

Similarly, attackers can gain access to employee usernames, software programs, department structures, geographical locations, and internal network architecture. 

As organizations often don’t realize that this information is revealed, their cyber risk exposure is significantly heightened. 

Recommendations for Security Leaders

• Establish metadata sanitization, retention, and usage policies and make these available to employees (securely, of course!). 
  

• Audit publicly accessible documents to identify risk exposure.

• Align forensic metadata collection processes with employee privacy rights and regulatory compliance requirements (e.g. GDPR).

• Preserve native files with metadata completely intact during incident response procedures. 

• Create chain of custody documentation to explicitly reference the preservation of metadata.

• Liaise with legal and compliance teams to ensure metadata retention aligns with disclosure requirements in litigation proceedings.

• Implement comprehensive, automated monitoring to detect unscrupulous activity or possible leaks from domains, allowing for the creation of threat intelligence about an organization’s attack surface and threat exposure pre-exploitation.

Metadata maintains a specific position in an enterprise’s security strategy. While useful in extensive forensic investigations, it presents an opportunity for malicious actors to exploit if mismanaged. Security leaders must therefore recognize its value as a forensic asset, and exercise proper due diligence regarding its management and exposure.