I know very little about JPEG.
Recently have a chance to get a little information on it.
Actually, image formats, video farmats have something call meta data.
Those data provide extra information for the content.
For JPEG, meta data is anything before the first ‘FFF1’.
There is where you can hide a virus inside.
It is another story for JPEG with digital water mark.
That, is some series professional shit which I do not need to know. XD