Due to its size, there has always been a fair amount of spam coming from UUNet. Lately however, the spam volume has become huge. UUNet has produced more spam than any other site on the internet -- over 147,000 posts since May in the small portion of Usenet which my filters monitor.
Item: 99% of posts from UUNet are spam. 
Item: 30-40% of all posts on netnews are spam, another 30-40% are cancels of that spam, and 20-30% are legitimate posts. This means that if the spam problem was eliminated, Netnews traffic would drop to as low as 1/5 of its present amount. 
Item: Before the UDP, there were 1.25 million spams per week, about half from UUNet.
Item: Before the UDP, UUNet alone accounted for roughly half of all netnews spam on the internet. This does not count spam originating from UUNet-hosted customers such as the Psychic Spammer or LibidoX
Item: Casual browsing will show that more than half the posts to the newsgroup Alt.sexual.abuse.recovery are spam, mostly porn spam including child pornograhy ads. You can imagine the effect this has on the regulars of this newsgroup. Many have abandoned the newsgroup because of this problem. At least one has gone back into therapy. UUNet is responsible for a good portion of this spam and steadfastly refused to respond to complaints.
Item: Most sexual discussion groups have been abandoned because of the level of porn spam in those groups.
Item: Before the UDP, UUNet rarely, if ever responded to complaints, except to issue an automated form letter.
Item: UUNet is the host for LibidoX, Online18, Netzilla, and Escort Guide, the four largest spammers on the internet.
For information on the legality of udp-style cancels, see this New York Times article. The article describes a massive cancel that came from UUNet last year, disrupting NetNews everywhere. (New York Times may ask you to register first, this is benign.)
In the last 24 hours (as of 5 Aug 1997, 14:26):
87,632 cancels issued for UUNet sources
85,869 of those issued for normal BI > 20 spam from UUNet
Therefore 97.9% of the traffic from UUNet during the last 24 hours was
cancelable as spam even without UDP considerations.
Again, some of the remainder may be spam. The remaining 1,763 messages would have to be examined by hand to determine whether they were spam or collateral damage.
[Update: the remaining messages have since been examined, with slightly more than half being spam. This brings the total up to 99%]
Here is a count of cancelled spam, top 20 sites, courtesy of Andrew Gierth:
417347 news1-alterdial.uu.net 95785 earth.superlink.net 58884 world1.bawave.com 55118 baker.se.highway1.com 49402 news0-alterdial.uu.net 27282 news.netdor.com 26118 news.eclipse.net 23973 news.online18.com 17731 mail.slutcom.ca 16332 news.worldnetla.net 15383 nylaw-07.nyls.edu 13633 roo.fosta.au 13092 max.imsis.com 11801 news.acadiacom.net 11378 184.108.40.206 11259 rig.ni.it 9864 vs04.vc-net.or.jp 9483 mtts01.Teleglobe.net 9385 storm.lightning.net 8263 buck.innerx.net
Here is a short summary of spam cancels against UUNet courtesy of "Uncle Roadkill"
Here is a longer-term history of weekly spam cancels previous to the UDP, courtesy of Andrew Gierth. These numbers reflect spams detected and cancelled. Usually some spam escapes detection and is not counted here.
|Week ending||cancels issued|
|7/14||82,951||(cancel moratorium in effect)|
Statistics provided by Ken Lucke, firstname.lastname@example.org. Spam-detecting software identified 97.9% of UUNet traffic as spam. Manual inspection of the remainder showed another 1.1% was also spam, leaving only 1% legitimate traffic.
According to Mat Dillon, sysadmin at Best.com, Netnews traffic is 1/3 spam, 1/3 spam cancels and 1/3 legitimate traffic. According to John Milborn, the numbers are 40% spam, 40% cancels and 20% legitimate traffic.
From email@example.com Wed Aug 6 21:59:25 1997 Return-Path: From: firstname.lastname@example.org Received: from server3.dont.telnet_here.com (1Cust48.max14.newark.nj.ms.uu.net [220.127.116.11]) Received: from localhost (root@localhost) by server3.dont.telnet_here.com (8.8.5/8.8.5) with SMTP id AAA01146; Thu, 7 Aug 1997 00:52:54 -0400 (EDT) Date: Thu, 7 Aug 1997 00:52:54 -0400 (EDT) Message-Id: <199708070452.AAA01146@server3.dont.telnet_here.com> Received: by server3.dont.telnet_here.com (bulk_mailer v1.6); Thu, 7 Aug 1997 00:28:06 -0400 Content-Length: 739 X-Lines: 20 Status: RO Authenticated sender is: email@example.com X-mailer: Wouldn't you like to know X-complaint-response: Go to hell To: undisclosed-recipients:; Message-ID:
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From firstname.lastname@example.org Fri Aug 8 13:16:17 1997 Return-Path:
Received: from Eng.Sun.COM by peregrine.eng.sun.com (SMI-8.6/SMI-SVR4) id NAA12682; Fri, 8 Aug 1997 13:16:17 -0700 From: email@example.com Received: from saturn.Sun.COM by Eng.Sun.COM (SMI-8.6/SMI-5.3) id NAA27167; Fri, 8 Aug 1997 13:16:14 -0700 Received: from www.kia.co.kr (www.kia.co.kr [18.104.22.168]) by saturn.Sun.COM (SMI-8.6/mail.byaddr) with SMTP id NAA25235 for ; Fri, 8 Aug 1997 13:16:15 -0700 Received: from www.kia.co.kr (1Cust59.max43.los-angeles.ca.ms.uu.net [22.214.171.124]) by www.kia.co.kr (8.6.12h2/8.6.9) with SMTP id FAA07645; Sat, 9 Aug 1997 05:02:48 +0900 Received: from mips-1.sailahead.com (mips-1.sailahead.com [126.96.36.199]) by sailahead.com (8.8.5/8.6.5) with SMTP id GAA05398 for ; Fri, 08 Aug 1997 12:11:32 -0600 (EST) Date: Fri, 08 Aug 97 12:11:32 EST To: firstname.lastname@example.org Subject: Cease And Desist Flaming Message-ID: <email@example.com> Reply-To: firstname.lastname@example.org X-PMFLAGS: 34666848 0 X-UIDL: 3273376668a65eb1890m0762123a Comments: Authenticated sender is Content-Length: 1607 X-Lines: 44 Status: RO On behalf of our client, Samsung America Inc., ("Samsung") we hereby request that you cease and desist all inflammatory internet hacking, telephone hacking, flaming, jamming, and other illegal activities. If you have responded aversely to a recent bulk email message from our client, Samsung America, Inc., or from any of its subsidiary companies, then you may be one of the people who has performed fraudulent and actionable transgressions, thereby causing severe harm to our client. Your email name was provided as being suspected of connection to various acts of internet terrorism. Your acts are illegal. Several messages have suggested that Samsung and/or its subsidiaries, including but not limited to Sailahead Global Emporium, www.sailahead.com, and Samsung Electronics, www.sosimple.com, violated US Federal Laws through activities commonly called "spamming." This allegation is unfounded in the law, as spamming is a protected activity under the laws of free speech. Our client has asked us to inform you that all of your future correspondences should be directed to their counsel: Russell L. Allyn, Attorney at Law California Sate Bar Number (SBN) 143531 Katz, Hoyt, Seigel & Kapor LLP Los Angeles, CA email@example.com 310-473-1300 310-473-7138 (fax) All incidents of internet terrorism will be prosecuted where possible, and reported to appropriate law enforcement authorities as warranted. Please consider this as your notice to cease all attempts to harm multi-national corporations who conduct legitimate commerce on the internet. Russell L. Allyn, Attorney at Law