After you open the suspect file in that sealed box, Dangerzone uses the open-source software LibreOffice to convert anything that's not already a PDF to a PDF format. It then uses the open-source software Poppler and ImageMagick to reduce that PDF further to red, green, and blue pixels. From those raw visual ingredients, it rebuilds the document in a second container, recreating a sanitized PDF with no hidden code, animations, or even web links. (Thanks to that pixel-rebuilding process, the software outputs a PDF regardless of the file format it takes in.) Dangerzone also uses the optical character recognition software Tesseract to convert letters and numbers in the PDF back to machine-readable text, letting you copy text from and search the file.
Think of it like taking a piece of paper that someone has sneezed on and putting it in a Xerox machine. The copy that comes out is visually identical to the original, but carries none of the potential risk of infection.
Also like that Xerox copy, the documents that Dangerzone produces aren't exact replicas. When WIRED tested an early version of Dangerzone, it worked perfectly to create sanitized PDFs out of most PowerPoint, Word, and PDF files, though it took as much as a few minutes in some cases to convert them. But other document types came out more mangled: GIFs, as you might expect, turned into non-animated, multi-page PDFs filled with some strange pixelated images on some pages. Excel spread sheets turned into collections of numbers and floating on white pages rather than a neat grid, and some PowerPoint slides were rotated 90 degrees for some reason. One PowerPoint with an embedded video resulted in a "Failed :(" message.
Despite those quirks and a few lingering bugs, Dangerzone represents a long-overdue attempt ..
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