Sunday 21 Jan 2024

DFG Found Damged Pictures

Image copyright

I have been using my tool, DFG, to monitor directories on my storage device for a while now. The purpose of this tool is to look for changes to pictures to help detect bitrot or other corruption.

Well, today, the tool failed hashes on 2 pictures from my 2023 directory. I have not edited these pictures so it’s time to explore.

Let’s call the pictures pic_1 and pic_2.

Here are the current hash values (these are incorrect so DFG highlighted this):

Hash File
e8df2ca352540bef8286778b8db7d57f7c2229e6d6cb8080f9d269a61a837429 pic_1
96c34792c95e85afe82679a68fa2318e83d5bb43cf8b320d77abb0f7f2278e8a pic_2

The hashes should be:

Hash File
32525262790a3841373070011ca533b4a81c26845fd25df07ae6e5a28cea9054 pic_1
42bc98f498e2612cef116dcd5eb26de3ac5a7f8c3f8db0b28fac4f7a39e950e9 pic_2

During my investigation I noticed the file sizes had changed too.

Should be 2.8 MB but changed to 2.2 MB.

I viewed the pictures together and noticed the a little has been cropped off from either side.

I checked Storj and downloaded the two files. However, the changed pictures were uploaded to Storj. At the time of writing, Storj does not allow object versions, so this was no use to me. I checked an external hard drive and restored the two pictures which were correct. When I backup to hard drives I do so with rsync copy with flags to not overwrite existing pictures, which stopped this corruption being replicated. As for Storj, I used rclone without flags to stop overwriting. So to prevent this in the future, I run rclone with the immutable flag.