Apple explains why it abandoned iPhone CSAM detection:

“Scanning every user’s privately stored iCloud data would create new threat vectors for data thieves to find and exploit,” Neuenschwander continued. “It would also inject the potential for a slippery slope of unintended consequences. Scanning for one type of content, for instance, opens the door for bulk surveillance and could create a desire to search other encrypted messaging systems across content types.”

“We decided to not proceed with the proposal for a hybrid client-server approach to CSAM detection for iCloud Photos from a few years ago,” he finished. “We concluded it was not practically possible to implement without ultimately imperiling the security and privacy of our users.”

One of the things which is interesting about this is that these are the exact arguments which campaigners against Apple’s scanning proposal used at the time – and the company seems to have listened.

And that Apple has made its reasoning public gives a strong imperative to it not to try the same thing again, which is a good sign for the future.