161 bytes hiding behind a photo

Both copies open as this same photo. One of them has a small ZIP archive, holding a one-line note, added after the end of the image.

• Before: the original photo.
• After: the copy with the ZIP added.

What changed

• The picture. Nothing. Viewers stop reading where the image ends.
• The end of the file. The original carries 151 bytes there, all recognised as the phone's own record. The copy carries 312, and some of it is not explained.
• What the file is. The copy is a valid photo and a valid ZIP archive at the same time.

What the report said: Security A for the original, D for the copy.

The report shows that something is there and what kind of thing it is. It doesn't say who put it there, or what the note says. This is crude hiding: content hidden carefully in the pixels of a lossless image is much harder to find, by any method.

Go deeper

• How to check a photo: How to find a hidden message or file in a photo
• Why it works: Building steganography detection, by Kenneth Springer
• Try it on your own photo