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):

The hashes should be:

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.