PNG File that is all black

[fiza]

We have been asked to look at a Student USB that has images on it but all the images are coming up black. The DSL has asked us to look. The image size is 30000x30000 pixels for all images.

Something very dodgy looking but we just cant decipher what is going on.

 

Has anyone come across something like this before?

 

Opening in Photoshop we can't see any layers but there is something not right.

Edited September 25, 2019 by fiza

[3s-gtech]

Is this “homework that been corrupted”? If so, it’s likely that the student has worked out a way of turning a blank file into a huge black png to pretend that the computer ate their homework.

 

If not, could possibly be a dying USB stick but I’ve never seen one act quite like that.

[georgeescott]

I’ve seen something similar when using a tool to compress/resize photos failed, resulting in all images becoming black. Never at 30000px though!

 

Is there any EXIF data in any of the photos?

[fiza]

Will check tomorrow about EXIF data. The issue is to do with safeguarding rather than homework. The DSL is suspicious as to what if anything is hidden in the black PNG files.

[rrrrr]

If you are suspicious about the files have you checked for steganography?

[fiza]

If you are suspicious about the files have you checked for steganography?

My colleague @DeGrimmy did look into that but we don't really know how to tell. Any ideas?

[SpreadsheetJockey]

Have you tried setting one of them as a desktop background or opening them in MSPaint? I think possibly you can use the alpha channel in photoshop to make something appear transparent that isn't.

[chazzy2501]

open it in notepad and see what the first few lines say.

[TechMonkey]

open it in notepad and see what the first few lines say.

 

Would be my first thought incase they are actually videos or documents with the file extension renamed. If too big for notepad try Notepad++.

[bald_pig]

Have you tried opening the file with 7zip? It's possible to hide archives in images.

[jthompson]

Perhaps check their browsing history for requests around the time of the files' timestamps.

[bald_pig]

Also found this:

https://superuser.com/questions/1224233/invisible-png-image-layer-that-is-only-visible-as-a-background