For the sake of clarity. This process isn’t DPI. Its content management. As the entire packet stream has to be assembled into its final format, these systems wouldn’t be analyzing the packets. They would reassembling the data portions of the packet (and ejecting the rest) and then analyzing the data for particular matches.

To understand the difference, this is the process Spam filters or e-mail content management systems use to enforce compliance rules. It may be a subtle distinction to the layman, but its an important distinction from a technology standpoint. (Not to say that DPI appliances can’t be used in conjunction with content management, they certainly can, but they are distinct application types.)

While some pedophiles who were smart would likely just resize images, I don’t imagine that authorities would have an issue chasing after the low hanging fruit using a DPI-facilitated method, and more traditional approaches for more intelligent pedophiles.

I’m a little leery of this method. Its very hard (if not impossible) to tag images. Resizing an image would invalidate any hash generated as a marker.

There would need to be a massive inventory of known child-porn images, and signatures generated. That signature database would have to be updated regularly and somehow distributed through secure (ie “tamper-proof” channels). If pedophiles are smart, they will resize the images in their collection (or change it from jpgs to gifs or combine images into one, etc. etc. Lots of free tools that will do this kind of process easily.) Any activity that changes the structure of the file.

So any use of hash signatures would rely on the criminals being stupid. A not unrealistic assumption, but this system would be very easy to defeat.