Introducing d-FIRST™

Validated and deployed by intelligence agencies around the world, Glasswall is the leader in the field of Content Disarm and Reconstruction. Our patented d-FIRST™ methodology creates safe, clean and visually identical files, mitigating the risk of malicious documents.

Step 1

Deep-File Inspection

deep-File Inspection takes the file and reads it into memory, inspecting the three distinct layers of the file:

  • Visual Content Layer – What users actually see when viewing or editing the file. The text and images on the page.  
  • Active Content Layer – Additional functionality in a  file  or program, such as Macros, JavaScript, embedded files or data connections.
  • File Structure LayerThe framework within which the Visual and Active Content is stored and managed.
Step 2


Remediation repairs a document’s structure, ensuring complete compliance with the specification set by the developer of that file type. For example, Adobe has an ISO 32000 specification that details all valid binary structures for PDF. The published specification for a file is what we call, ‘known good’. 

Step 3


Sanitisation is the removal of Active Content, mitigating the risk posed by unnecessary functional features in files. Controlled by policy, sanitisation allows users to get the document features they need and strips out all the functions they don’t. 


Supported File Types

Glasswall’s core engine regenerates the following file types

Category File Type Extensions
Microsoft Office (Legacy)
  • Microsoft Word
  • Microsoft Excel
  • Microsoft PowerPoint
  • doc, dot
  • xls, xlt
  • ppt, pot, pps
Microsoft Office (2007+)
  • Microsoft Word
  • Microsoft Excel
  • Microsoft PowerPoint
  • docx, dotz, docm, dotm
  • xlsx, xltx, xlsm, xltm
  • pptx, potx, ppsx, pptm, potm, ppsm
  • Adobe PDF
  • pdf
  • jpeg
  • png
  • gif
  • jpeg, jpg, jpe
  • png
  • gif

Microsoft Office binary file type specification

Microsoft Office XML file type specification

PDF file type specification

Active Content That Can Be Sanitised

PDF Files Office Files
  • JavaScript
  • Acroforms
  • External Hyperlinks
  • Embedded Files
  • Metadata
  • Actions
  • Internal Hyperlinks
  • Embedded Images
  • Macros
  • Review Comments
  • External Hyperlinks
  • Embedded Files
  • Metadata
  • Dynamic Data Exchange (Word & Excel only)
  • Internal Hyperlinks
  • Embedded Images

Try Our Technology

Upload a file.
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Glasswall Products





Glasswall's award-winning technology is available across a number of platforms and services,
delivering safe, clean and visually identical files in any business process.