Aioe.org tries to reject spam messages sent to newsgroups using cleanfeed, an old antispam software written in perl. It plots a nice html statistical page that is printed below. Everybody should consider that these data do not represent a reliable sample of the number of spam messages actually posted on usenet because they only refer to this server.
Filter started: Wed Jul 6 06:21:41 2022
Report generated: Fri Aug 12 20:02:33 2022
Uptime: 3246052 seconds
Accepted: 628259
Rejected: 63984
Refused: 17
Period since last report: 3602 seconds
Articles examined (this period): 0.1/s
Articles accepted (this period): 0.1/s
Articles examined (entire uptime): 0.2/s
Articles accepted (entire uptime): 0.1/s
MD5 entries: 283 Rejecting: 34
PHL entries: 441 Rejecting: 5
PHN entries: 355 Rejecting: 8
PHR entries: 0 Rejecting: 0
FSL entries: 366 Rejecting: 0
MID history: 355
Supersedes entries: 0