I’ve heard only some weeks ago about extracting the original thumbnail (created by digital camera) from a jpeg picture.
It’s easy to realize that in a thumbnail you can find particulars that are being removed from the published version of the picture; you can find some examples of what i’m trying to say here and here.

I’ve made a simple bash script that uses the exif binary (so you need it to use that script), the script has three parameters:

exif_thumb_extractor.sh [-r] <pictures_dir> <target_dir>

* -r option it’s for new recursive mode!

Enjoy it and download :)