this post was submitted on 28 Aug 2023
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WARNING: Lemmy Self-Hosters, There Have Been CSAM Attacks taking place against !lemmyshitpost@lemmy.world (jamie.moe)
submitted 1 year ago* (last edited 1 year ago) by Jamie@jamie.moe to c/selfhost@lemmy.ml
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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.

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[–] Mic_Check_One_Two@reddthat.com 31 points 1 year ago* (last edited 1 year ago) (1 children)

Was going to say the same. Windows and Linux both use “lazy” ways of deleting things, because there’s not usually a need to actually wipe the data. Overwriting the data takes a lot more time, and on an SSD it costs valuable write cycles. Instead, it simply marks the space as usable again, and removes any associations to the file that the OS had. But the data still exists on the drive, because it’s simply been marked as writeable again.

There are plenty of programs that will be able to read that “deleted” content, because (again) it still exists on the drive. If you just deleted it and haven’t used the drive a lot since then, it’s entirely possible that the data hasn’t been overwritten yet.

You need a form of secure delete, which doesn’t just mark the space is usable. A secure delete will overwrite the data with junk data. Essentially white noise 1’s and 0’s, so the data is completely gone instead of simply being marked as writeable.

[–] lazynooblet@lazysoci.al 3 points 1 year ago (2 children)

Would rm be okay if you regularly fstrim?

[–] alanceil@lemmy.world 4 points 1 year ago* (last edited 1 year ago) (1 children)

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.

[–] Anaralah_Belore223@lemmy.world 1 points 1 year ago

Or physically destroy the whole drive altogether.

[–] Zacryon@feddit.de 2 points 1 year ago

TRIM tells the SSD to mark an LBA region as invalid and subsequent reads on the region will not return any meaningful data. For a very brief time, the data could still reside on the flash internally. However, after the TRIM command is issued and garbage collection has taken place, it is highly unlikely that even a forensic scientist would be able to recover the data.

From: https://en.m.wikipedia.org/wiki/Trim_(computing)#Operation

So: probably yes.