http://trashchan2rvdng5zm7346sfxrrkjwvqzolw4lfdyldcsdpmsyj4dkid.onion/meta/catalog.html
Here is the monitoring system: https://xj9k.neocities.org/ It only monitors certain sites, and only OPs on some sites, so it's far from conclusive but it's demonstrative.
Spam posts are grouped together under one detection (semi-automatically, so there are some small mistakes), it's worth clicking [Expand] and seeing how they differ over time and attempt to evade filters, or how the same spammer makes similar but different spam posts.