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225

As mentioned in the answers to a very similar question, scribbling over part of an image will destroy the original pixels, assuming that your editor doesn't store any layers or undo history in the saved image. (Paint doesn't.) There are some things to watch out for, though: The width of the blanked region places an upper bound on the length of the secret ...


191

Yes, it can be recovered. As long as shutter does not use layer (it almost certainly does not) and as long as the black is really all black (it must not be transparent), it is enough. The picture that you provided uses some amount of transparency, see here: All I had to do is use the Fill tool in MS Paint. If I used some algorithm that would take the jpg ...


137

Summary: The most likely explanation is that the old text was removed by using a fuzzy or smooth eraser tool. Analysis: In the image below I have only increased brightness and contrast to make the "hidden message" more visible. Nothing fancy. The slight red tint is only due to the fact that the black background of the original has a very slight red ...


113

Other answers give a good technical explanation but let me try with an analogy: Please send your credit card number to scam@example.com Did you read it? Did you do it? It's more or less the same for your CPU. Reading something is not the same as executing it.


81

The other answers mostly talk about attaching arbitrary code to images via steganographic techniques, but that's not very interesting since it requires that the user be complicit in extracting and executing that. The user could just execute malicious code directly if that's their goal. Really you're interested in whether there's a possibility of unexpected,...


80

You don't even need to use an image editor in this case to recover the "redacted" text. Simply zooming in on the image is enough to read it. So I would say that yes, it most certainly is possible to recover the original text.


71

In this case the image can be recovered very well As others already pointed out the dark patch is not completely black. It has a transparent effect and only darkens the original image. The original image can be recovered almost completely: In this case the recovery was pretty straightforward. I needed to check the range of grey levels of the patch and re-...


64

Ditto Ben N, but let me add a couple of points that are too long to fit as comments. I'd emphasize the distinction between layered and un-layered data formats. Drawing a black box over a section of a GIF, JPG, or PNG image destroys the previous contents. Drawing a black box over a section of a Photoshop, Corel Draw, or Paint Shop Pro native image does not ...


64

CPU instructions are given in what are called opcodes, and you're right that those live in memory just like your image. They live in conceptually different "areas" of memory, though. For instance, you could imagine an opcode "read" (0x01) that reads a byte of input from stdin and puts it somewhere, and another operand "add" (0x02) that adds two bytes. Some ...


58

Can you send them? Yes, of course. Just assemble them and stick them somewhere in the image file. Will the target execute them? No, not unless you already have control over the target (and can thus put a program there to read and execute them), or you find some exploit in an image viewer and get the image to load in it.


46

Usually the PNG format does not support multiple layers. So when you draw over something, whatever was there before is lost. However, the PNG format supports storage of an unlimited amount of metadata which is usually not displayed by image viewers. This feature is often used by image editors to add additional metadata to the image. One possible use-case is ...


43

At first I thought this was simply a hoax as no digital image process I'm aware of could do this by accident, but I was intrigued. Taking the orignal image and performing an equalize on it did indeed pull out the alternate fragments. It also revealed the black background to be not really black but a composite of dense subtractive primary colors. Here's a ...


39

Based on the description at Virustotal you've linked to this is in reality not an image, but a real PE32 executable (normal windows executable). So only the file name extension was changed to hide the real purpose of the file. PE32 will not be automatically executed when they have the .jpg extension like in this case. Also the image viewer which will be ...


33

You could if your target used a version of Internet Explorer from before August 2005 to view a JPG. Or if they were going to open a PNG in Windows Media Player on Windows 98 with no security updates installed. And so on. There was a lot of old software that used to have bugs where, if you made an image file in which the first part of the image file lied ...


29

Yes, the text can be unmasked, either by simply zooming in or using any of the techniques - but not restricted to - pointed by pabouk and Peter answers. I have clearly asked for the correct/most secure way of producing photographic evidence. Completely remove any sensitive data from print-screens. Steps Press the PRT SCR button on your keyboard (...


22

When blacking out sensitive information in Paint the original pixels are destroyed. But using Inkscape to black out part of a vector image does not destroy the pixels, but instead covers them. If someone removes the black cover they can see the pixels. The same applies to things like Foxit Reader (I almost sent a document with sensitive information which had ...


17

As a raster image program that does not use layers nor contain an undo history after saving, overwriting sensitive pixels in Paint irrevocably changes them in the saved image. More reasoning: Microsoft Paint is a proven simple piece of software with a long history and great popularity that works natively in simple raster image file formats. Serious flaws ...


13

Already a few good answers here, saying Paint is safe. (I have no reason to believe otherwise.) Just want to add that while blacking out a rectangle that fully covers the area and any surrounding areas (lists that information is part of etc) using a basic well studied image editing program should be fairly safe, just using any image editor might not be ...


12

Yes, there are ways to 'exploit' buffer overflows. Sometimes the code may need to be executed via a separate script, and in theory you could assemble a virus from multiple images that contained code hidden within the picture using stenography but there are easier ways. Basically many computer systems expected images to comply with the exact specification ...


12

When you paint over a jpg or png file, you are not putting a sticker over the image, you are more ripping a hole on the image and filling the hole with ink. Even on Photoshop, if you export the picture as jpg it will flatten the image, merging all layers together and destroying the original obscured area forever. There's no way to reconstruct the original ...


12

No, it's not. Although SVG files can contain JS (see this), these will only get executed if: the user directly visits the .svg file in their browser the image is embedded within <embed> tags. Modern browsers will never execute scripts in SVGs if it's within <img> tags. And even in the two cases above, the server can provide CSP headers ...


11

Re. question 1: This does not look like a JPG at all. It has the magic "MZ" characters at the beginning of the file that signifies "Windows Portable Executable File". Also your VirusTotal report points in that direction: simply an EXE file that does not actually have ".EXE" as the file name suffix. In contrast a JPG file should ...


11

Examples As shown above, your example was breakable,the blacks of the redaction had variation showing the text. Real life example New York Times Suffers Redaction Failure, Exposes Name Of NSA Agent And Targeted Network In Uploaded PDF This was an example of a PDF that appeared redacted, but the data could be recovered. Ways data can leak Document titles ...


11

No. Image files such as JPEG files don't execute code, they are simply rendered and displayed. If you want to hide some information in a file that's called Steganography, but that only hides information, it doesn't execute any instructions. For a file to run code it has to be an executable, or be run by another program which reads the file, then executes ...


9

I expect the explanation is fairly mundane. An image was probably prepared with 3 layers: Background colour and maybe the footer text Trump text Biden text You could then produce both messages with the same look by hiding either layer 2 or layer 3. I imagine what happened here is the person preparing the images hid layer 2 by reducing the opacity and ...


8

Take a look at this fantastic blog post that was recently published by security researcher Robin (@digininja) about this exact topic: Direct view with content-disposition: attachment - not vulnerable - Headers are sent to force the file to be downloaded. Direct view with CSP - not vulnerable - The Content Security Policy is set to disallow inline ...


8

I think you may be misusing what's meant to be a highlight tool (I'm not at any of my Ubuntu machines ATM and don't have shutter installed anyway to test). I can't quite believe that a tool meant for redacting would have such an obvious flaw as working with transparency takes more effort than not). In the GIMP you can select an area and fill that area ...


8

Don't provide screnshots. Provide descriptions OR sample screenshots taken at times when sensitive data is not on the screen, with description that "X appeared here". "It's no evidence!" you may say. BUT - a screenshot that had been redacted is also not an evidence. It's just a product of your artistic skills. Your testimony of the situation usually carries ...


7

Some comments on previous answers (all good - Stack Exchange is like watching really good crossword puzzle players.) An interesting topic which occasionally might be life-and-death important. (My overactive imagination at work, but battered women at a shelter whose location is critical to keep secret are an example that come to mind). Points that I hadn't ...


7

No, the security is no better. The typical formats used for screenshots (JPEG or PNG) are not image formats that support layers like say, a PSD does. When you add the green scribble, you're not adding a layer, you're replacing part of the image. The extra step, the screenshot-of-a-screenshot should give you an image file that's materially the same. ...


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