There have been users spamming CSAM content in !lemmyshitpost@lemmy.world causing it to federate to other instances. If your instance is subscribed to this community, you should take action to rectify it immediately. I recommend performing a hard delete via command line on the server.
I deleted every image from the past 24 hours personally, using the following command: sudo find /srv/lemmy/example.com/volumes/pictrs/files -type f -ctime -1 -exec shred {} \;
Note: Your local jurisdiction may impose a duty to report or other obligations. Check with these, but always prioritize ensuring that the content does not continue to be served.
Update
Apparently the Lemmy Shitpost community is shut down as of now.
No, fstrim just tells your drive it doesn’t need to care about existing data when writing over it. Depending on your drive, direct access to the flash chips might still reveal the original data.
If you want ensure data deletion, as OP said, you’ll need to zero out the whole drive and then fstrim to regain performance. Also see ATA Secure Erase. Some drives encrypt by default and have Secure Erase generate a new key. That will disable access to the old data without having to touch every bit.
Or physically destroy the whole drive altogether.