Handling media in case of illegal content

[CaptainMalu]

Description:

In Germany we have some "nice" laws against CP.
https://www.gesetze-im-internet.de/englisch_stgb/englisch_stgb.html#p1813

Which lead to the following problem: https://www.lawblog.de/archives/2023/05/12/lustiger-gruppenchat-mit-bitterem-ende/

If the user (recipient) is in a group chat and someone (sender) posts CP, the user (recipient) could go to jail if he doesn't delete the file immediately.

As far as I understand synapse and matrix media works as follows.
A evil user uploads a file to his homeserver. This HS creates a media id. If the user posts this file into a room there will be an event with a link to this specific file.
Now all remote HS (running synapse) in this room will download this file (only when viewed?).
So far so normal.
But if this content is problematic a room admin will most likely delete the event.
So the users in this room can't see the file anymore.
But as media can only be deleted from server admins the file will stay on the remote servers in the remote media repo.
As most server admins are only normal users in big federated rooms they'll most likely not know there was a problematic file in the deleted event and they wouldn't know the media id to delete it manually.
And most of us have some other users on the server to which could be also part of federated rooms, where the server admin wouldn't even noticed that there was an event deleted.

So it would be nice to have a system which helps to delete such files.
Maybe a notification with (a list of) media IDs which have to be checked?
A more automatic deletion would be nice but technically not possible?

Edited to make clear that I'm looking from the point where someone would unwillingly get into the position to possess CP.

[jimmackenzie]

This is a thoughtful issue!

Like you point out, when room moderators redact illegal content, it is no longer accessible to users in the room. The server admins will have some extra work¹ depending on their jurisdiction and the content. The moderator should inform the homeservers who are participating in the room that they redacted a piece of illegal content — that is currently a manual task, and we should make it easier. Your suggestion of a notification with the media ids feels like a good place to start exploring.

We have some adjacent experiments underway, so we'll think about this as part of that process.

Footnotes

1. Investigating the report, quarantining the media using the media quarantine API, action against the uploader, mandatory or voluntary reporting to name a few considerations ↩