Are there any measures to prevent CP or other unlawful images from being uploaded to the site?
Posted under General
If you see child porn (with actual children, not drawings of what appear to be children), flag it and it will be permanently deleted.
If you see pornographic drawings of what are clearly (pre- or very early adolescent) children, just add the appropriate tag(s) of toddlercon, loli and shota if they are not added already.
Updated
"Illegal content" in a broad sense is difficult to define, since the site is used globally and different content is banned in different jurisdictions. For instance, everything in the uncensored tag is considered obscenity in Japan.
Uploads are manually moderated. If you see something seems illegal, you can report it to an admin.
There's no automated system to prevent illegal content from being uploaded because there's no easy way to automate it. There are some organizations who have databases of image hashes of CSAM material, but they don't usually make those available to the public or to sites like us.
Note that all photographs of people under the age of 18 are against the rules, regardless of content. Not allowing photos in general avoids most of these problems.