Testing an image directory for hidden rars?

How would someone go about quickly testing each and every image to see if it had a rar or any other file hidden inside of it? What language would be best for doing this, if a tool isn't already available?

See http://www.jpeg.org/public/jfif.pdf - use it to write a program that determines what the size of the file should be. If the file is larger than that, then there is the hidden data.