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It sure seems like this is two different techniques/technologies at work. There is a CSAM deterctor using a known database and then, it looks like, there is a separate model in messages for detecting pornographic content without a known database.

It doesn't sound like it can "detect pornographic content" since the difference between pornography and nudity is not going to be reducible to a coefficient matrix.

Yeah but that just blurs the image and notifies the parents. Pretty low impact for false positives.

Sorry for the confusion — I was referring to just the CSAM hash feature that uploads results to iCloud.

There is also scanning for nudity in the Messages app, but those scans happen on-device and the photos stay on-device even if nudity is detected.