PhotoDNA

PhotoDNA, developed by Microsoft in 2009 in collaboration with Dr. Hany Farid, initially at Dartmouth and now at Berkeley, is a forensic technology aimed at identifying and eliminating child sexual abuse material online. This system uses "fuzzy image matching" or "fingerprint" technology, enabling it to detect altered images, such as those cropped, colored differently, or slightly modified, which traditional cryptographic hash methods couldn't catch. This adaptability makes PhotoDNA a robust tool for maintaining the integrity of image recognition despite minor alterations. The technology, while proprietary, is widely used by major tech firms like Google and Facebook to bolster their detection systems, though it's not open source to prevent potential misuse by those attempting to evade detection systems 1.