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Newsgroups: comp.risks
X-issue: 6.21
Date: Wed, 3 Feb 88 05:40:15 EST
From: mnetor!utzoo!henry@uunet.UU.NET
Subject: Risks of helpful news software

This one is old news on Usenet, but may not be so well-known elsewhere.
Normal Usenet newsgroups are "unmoderated", i.e. anyone at a Usenet site
may post contributions without having to route them through a moderator
for approval.  Postings propagate via a "flooding" broadcast protocol:
when a site receives a new posting, it sends the new posting to ALL other
sites that exchange news with it.  There are some other provisions that
break loops and prevent duplications.  Normally, this works pretty well;
it is much more efficient than point-to-point mailing lists for traffic
that is read by many people.  (A minor variation on this method is now being
used on parts of the Internet as well.)

Relatively recently, an attempt has been made to provide better support
for moderated newsgroups, which still use the flooding protocol but which
do clear all submissions through a human moderator first.  (Some Arpanet
mailing lists are gatewayed onto Usenet as such groups.)  Modern versions
of the news software will either post a user's followup or mail it to
the moderator, depending on the nature of the newsgroup.  Now, the older
versions did not do this, and Usenet's lack of central authority makes it
impossible to enforce coordinated software upgrades, so there are backwaters
of the net where this doesn't work.  Like the phone company, Usenet has to
be backward compatible nearly forever.  To minimize loss of submissions at
boundaries between new software and old, while enforcing the all-postings-
via-moderator rule, the new software also mails to the moderator (rather
than posting) when an article arriving from another site is in a moderated
newsgroup and is not marked "approved by moderator".

Of course, this means that if such an article somehow gets posted at an
old-software site with several paths to new-software sites, the poor
moderator gets N copies of it.  This can be anything from a nuisance to a
disaster, depending on the value of N and how frequently it happens.  Some
Usenet moderators nearly quit in disgust shortly after the new software
first came out, when new-old boundaries were common.  It's less of a problem
now, but still crops up on occasion:  due to a complex combination of
mistakes on my part, a routine contribution to Risks from me got posted
instead of mailed here (we run new software but in an unusual configuration),
and PGN got six copies of it at last count.  (Sorry about that, Peter.)

When thousands of sites run software that is willing to send network mail
automatically to specific individuals, those individuals can have a very
rough time of it if the software does something unexpected...

Henry Spencer @ U of Toronto Zoology {allegra,ihnp4,decvax,pyramid}!utzoo!henry

   [The volume of barfmail continues to be quite painful, particularly
   from addresses that have worked consistently in the past.  I am therefore
   instituting a more Draconian policy of simply not trying to track down
   these problems.  If I don't hear from you when you STOP getting RISKS, I
   can only assume that you don't care.  (But don't panic if a week goes by
   without your RISKS FIX.  There are weeks when I cannot get to it.)  

   A sample of recently barfed addresses includes, ...@VLSI.JPL.NASA.GOV,, 
   ...@ADS.ARPA, ...@JPL-MIL.ARPA, ...@ACATT1.ARPA, and
   <BBOARD>RISKS.TXT@ECLC.USC.EDU (No such mailbox!).  PGN]

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