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: Sat May 14 08:04:32 2022
Report generated: Sun May 22 10:25:01 2022
Uptime: 699629 seconds
Accepted: 123710
Rejected: 12414
Refused: 115
Period since last report: 3632 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: 867 Rejecting: 23
PHL entries: 216 Rejecting: 2
PHN entries: 201 Rejecting: 10
PHR entries: 0 Rejecting: 0
FSL entries: 427 Rejecting: 0
MID history: 266
Supersedes entries: 0