 <p>You can certainly use all the tools in PIL to figure out if an image has been modified. The problem is that figuring out is a very complicated task, so there is no easy, already implemented, method that you call and it tells you if the image has been manipulated. </p> <p>You should read some papers on this topic just to see how difficult that is. After that you may (or not) want to implement the ideas presented in those papers using PIL.</p> <p>Here's a <a href="http://scholar.google.com/scholar?q=identifying+image+manipulation&amp;hl=en&amp;btnG=Search&amp;as_sdt=1%2C5&amp;as_sdtp=on" rel="nofollow">link</a> with a search for such papers.</p>