Headlines and blog articles are currently making the rounds claiming that Apple scans images displayed in Finder starting with macOS 13.1. It's claimed that this is the CSAM scan searching for Child Sexual Abuse Material.
Although or precisely because Apple made it clear last year that they would not search for images and videos showing child sexual abuse on iOS, in iCloud, on Mac, and elsewhere, the topic is being brought up again. The trigger is the data exchange with Apple servers via the mediaanalysisd process in macOS. But this has nothing to do with it.
CSAM Scan Confusion and mediaanalysisd in macOS 13.1
The discussion arose because it was observed on some Macs that mediaanalysisd had established or wanted to establish a connection to an Apple server. Due to the frequent headlines and articles about CSAM scanning and potential nude image detection on devices last year, some users became alert again because of mediaanalysisd and were led to the hasty assumption that the CSAM scan had now been implemented after all.
Media Analysis is Not Nude Image Detection
What's interesting to observe is that this connection is made without technical derivation. The statement that mediaanalysisd and CSAM scan are connected is not preceded by a deeper look into the matter. That alone is an indication that something is wrong.
Because those articles and reports that contain an analysis of the process code and network exchange come to the conclusion that media analysis is the process that has been used for years for person, animal, and object recognition as well as for the "Live Text" feature for text recognition in images. And this doesn't use unencrypted image content, but hash codes.
Source: The Eclectic Light Company
Conclusion on the Topic
No, Apple has not secretly installed a nude image scanner on Mac with mediaanalysisd. Media analysis has been a component of Apple systems for years, from which users also benefit daily. Whether through person search in the Photos app, through text recognition in current operating systems, through the ability to look up image content like plants, animals, and art in online encyclopedias, or similar features.
A brief research and reading of technical analyses of the process show that only encrypted codes are transmitted for this, not raw image content or even copies. Privacy is preserved and law enforcement agencies are not given an unnecessary backdoor for surveillance. So two contemporary things were connected that have no real connection.