One of the most useful (yet possibly underutilized) data assets returned by DomainTools Iris is the screenshot. Analysts interactively reviewing sites and comparing screenshots (or other images) can use traditional cryptographic hashes to find exact image matches, but many analysis targets may intentionally make small changes (perhaps slightly resizing images or tweaking just a few pixels in images) in an effort to avoid detection by traditional cryptographic hashing approaches.
Fortunately, perceptual hashes make it easy to empirically and objectively assess images that we can see look quite similar, even if they may differ slightly in inconsequential ways. We can even use perceptual hashes as a way to identify clusters of likely-related sites.
In this white paper: