This App Makes Even the Sketchiest PDF or Word Doc Safe to Open

Word documents, and even PDF files, aren't necessarily safe. These normally innocuous files can be injected with malicious “poison” code or simple scripts of code that can be a serious security risk.

You probably already know it's dangerous to open files from sources you can't necessarily trust. If you're an activist or journalist—or anyone who occasionally depends on anonymous tips to do their jobs—you might run into a situation where potentially useful information is inside a Microsoft Word document or PDF file that you can't exactly vouch for. Wouldn't it be nice if you could open those files and read them without exposing your device to potential security risks?

Dangerzone is a free and open source tool built for this purpose. Originally built by journalist and security engineer Micah Lee, this application opens files in a sandbox environment with no internet access, then converts the file to an image-based PDF with no scripting enabled. The resulting PDF has any malicious code stripped out and should be safe to open—at least, as safe as anything can be.

"You can think of it like printing a document and then rescanning it to remove anything sketchy, except all done in software," explains the about page, which includes a lot of fascinating details about how the application works.

To get started, download and install Dangerzone. There are downloads for Windows, macOS, and various Linux systems. The first time you run it there will be a brief setup, after which you can simply drag files to the window.

The application can open and convert PDF, Word, Excel, PowerPoint, Open Office, EPUB, and image files. You can drag and drop multiple documents at once, if you'd like.

After adding documents you will be asked a few questions: where you'd like the resulting files to end up, whether they should open after the conversion is done, and whether you'd like to use optical character recognition (OCR) in order to make the document searchable. You can also move the original, potentially unsafe documents into a subfolder named "unsafe," helping ensure you don't confuse them with the newly made safe ones.

Hit the Convert to Safe Document button when everything looks good, and the application will get to work making a safe version of your documents.

It's all very simple to use, which is the point. But the technology behind takes multiple steps. First, Dangerzone loads up a container (on Linux) or a virtual machine (on Windows or macOS). This subsystem has no access to anything else on your computer—not even the internet—meaning the file won't be able to run any scripts, see any of your data, or track your activity in any way. Next, the application uses open-source tools to convert the file into a PDF, then convert every page of that PDF into pixels, meaning there's no scripting or even text in the resulting document. Then, optionally, the resulting PDF is scanned in order to add OCR data, giving you a searchable PDF.

You might think this is overkill, and depending on what you do for a living it might be. But there are perilous times, and anyone working on sensitive matters should use every tool at their disposal to stay safe. Keep this one in mind the next time you're not quite sure whether you should be opening a particular document.