I have no idea how much this costs but some bigger companies use Microsoft PhotoDNA [1] For text strings I think you could just write scripts to regex search y

I have no idea how much this costs but some bigger companies use Microsoft PhotoDNA [1] For text strings I think you could just write scripts to regex search your databases/text-files for that. People will evade it with UTF symbols unless you block all except specific UTF characters. If your service is free I think your options may be very limited. To my knowledge there are no open source projects to identify what you are looking for. Some smaller sites will ban specific binary file hashes but the people that use your site will quickly figure that out and evade it by re-encoding their files. Perhaps one risky option would be to find a cloud storage provider that does CSAM scanning and use that as block storage for your site. I say risky because in the eyes of that provider you are the one uploading the files, so you would need to have lawyers and contracts in place that specify the purpose of that integration and be ready to be accused of storing illegal content. [1] - https://www.microsoft.com/en-us/photodna https://www.microsoft.com/en-us/photodna