If you used pixelation to redact sensitive information, you may want to use a different method, as a security researcher has developed a new way to successfully recover pixelated words from redacted documents.
Senior researcher at security firm Bishop Fox, Dan Petro, published a new blog post detailing how he was able to fully recover the text from an image that was redacted using the rasterization method.
While the media and researchers often use pixelation or blurring to hide text in sensitive images posted online, Petro has shown that it is much safer to use opaque bars to hide text.
Petro began his research on how to recover pixelated words from redacted documents after Jumpsec Labs launched a challenge open to anyone to decipher the text in a pixelated image. After researching a number of pixelation and unclogging techniques, she found a solution to the challenge and sent his findings to Jumpsec Labs.
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Although there are a number of photo editing tools to improve pixelated images of people or landscapes, until now there was no tool capable of recovering the text found in pixelated images.
For this reason, Petro and Bishop Fox released a new open source tool on GitHub called Unredacter. The tool can correctly reconstruct the original text of a document in its entirety if it has been redacted using rasterization.
Petro provided additional information on how users who need to type text into a document should do so in his blog post, saying:
"The bottom line is that when you have to write text, use black bars that cover all the text. Never use anything else. No pixelation, no blur, no blur, no swirls. Oh, and make sure you change the text as an image. Don't commit the error of changing your Word document to have a black background with black text.
Fortunately, many of the best PDF editors, like Adobe Acrobat DC, already offer the ability to redact text on sensitive business documents.
Via BleepingComputer