I noticed a bit of panic around here lately and as I have had to continuously fight against pedos for the past year, I have developed tools to help me detect and prevent this content.
As luck would have it, we recently published one of our anti-csam checker tool as a python library that anyone can use. So I thought I could use this to help lemmy admins feel a bit more safe.
The tool can either go through all your images via your object storage and delete all CSAM, or it canrun continuously and scan and delete all new images as well. Suggested option is to run it using --all once, and then run it as a daemon and leave it running.
Better options would be to be able to retrieve exact images uploaded via lemmy/pict-rs api but we’re not there quite yet.
Let me know if you have any issue or improvements.
EDIT: Just to clarify, you should run this on your desktop PC with a GPU, not on your lemmy server!
This is extremely cool.
Because of the federated nature of Lemmy many instances might be scanning the same images. I wonder if there might be some way to pool resources that if one instance has already scanned an image some hash of it can be used to identify it and the whole AI model doesn’t need to be rerun.
Still the issue of how do you trust the cache but maybe there’s some way for a trusted entity to maintain this list?
How about a federated system for sharing “known safe” image attestations? That way, the trust list is something managed locally by each participating instance.
Edit: thinking about it some more, a federated image classification system would allow some instances to be more strict than others.
I think building such a system of some kind that can allow smaller instances to rely from help from larger instances would be extremely awesome.
Like, lemmy has the potential to lead the fediverse is safety tools if we put the work in.
Consensus algorithms. But it means there will always be duplicate work.
No way around that unfortunately
Why? Use something like RAFT, elect the leader, have the leader run the AI tool, then exchange results, with each node running it’s own subset of image hashes.
That does mean you need a trust system, though.
As I’m saying, I don’t think you need to: manually subscribing to each trusted instance via ActivityPub should suffice. The pass/fail determination can be done when querying for known images.
Yeah that works. Who is the leader and how does it change? Does Lemmy.World take over because it’s largest?
Hash the image, then assign hash ranges to servers that are part of the ring. You’d use RAFT to get consensus about who is responsible for which ranges. I’m largely just envisioning the Scylla gossip replacement as the underlying communications protocol.
You could just save a hash of an offending image. Much shorter list, more efficient, etc.
I’d rather have a text-only instance with no media at all. Can this be done?
Yes it is definitely possible! Just have no pictrs installed/running with the server. Note it will still be possible to link external images.
My understanding was it’s bad practice to host images on Lemmy instances anyway as it contributes to storage bloat. Instead of coming up with a one-off script solution (albeit a good effort), wouldn’t it make sense to offload the scanning to a third party like imgur or catbox who would already be doing that and just link images into Lemmy? If nothing else wouldn’t that limit liability on the instance admins?
I was thinking the same thing. Stop storing the images and offload to Imgur or whatever. They likely already have a solution for this issue. Show images inline instead of a link. Looks the same, no liability.
Saying that, this is tremendously cool. I was given pause though by another poster on the thread mentioning the legality of using this in the U.S.
Might be what we’d need to do for small servers lacking moderation, wanting to avoid the liability from potentially hosting harmful images.
I used postimg.cc when hosting was having issues, I’ll probably use it more to ease up Lemmy admins’ jobs.
TBH, I wouldn’t be comfortable outsourcing the scanning like that if I were running an instance. It only takes a bit of resources to know that you have done your due diligence. Hopefully this can get optimized to get time to be faster.