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: Tue Jul 20 12:08:53 2021
Report generated: Tue Aug 3 10:44:07 2021
Uptime: 1204514 seconds
Accepted: 188857
Rejected: 33382
Refused: 114
Period since last report: 3610 seconds
Articles examined (this period): 0.1/s
Articles accepted (this period): 0.1/s
Articles examined (entire uptime): 0.1/s
Articles accepted (entire uptime): 0.1/s
MD5 entries: 272 Rejecting: 23
PHL entries: 374 Rejecting: 2
PHN entries: 280 Rejecting: 5
PHR entries: 0 Rejecting: 0
FSL entries: 341 Rejecting: 0
MID history: 477
Supersedes entries: 0