Message from discussion Improvement of Cancel Processing

Path: g2news1.google.com!news3.google.com!fu-berlin.de!uni-berlin.de!not-for-mail
From: n...@individual.net (NetNews Team Individual.NET)
Newsgroups: alt.usenet.news-server-comparison
Subject: [Individual] Improvement of Cancel Processing
Date: 28 Jun 2007 12:00:00 GMT
Organization: Freie Universitaet Berlin
Lines: 84
Message-ID: <2007-06-28.Cancel2.0-en@fu-berlin.de>
X-Trace: news.uni-berlin.de niXSbdmih1eZKVwe9TpISAsJ33PDjbYDiuT86vPHjWGpbZcU78kO3v

The system of Cancels and Supersedes in Usenet (removing and
overwriting articles) existed since the ancient times of early
electronic communication and relied - without special validation and
protection - on the sense of responsibility and good faith of all
Usenet users. Unfortunately, with growing numbers of Usenet
participants and years passing by, this cannot be assumed anymore.

During the last months, we noticed a strong increase of rogue Cancels
and rogue Supersedes in the German language hierarchy de.* as well as
- with significant higher numbers - the Big-8 groups, including very
sophisticated methods of obfuscation and appearance which make it
almost impossible for an avarage Usenet user to even notice or
understand what happened. As a consequence of this incidents, we made
the decision to stop the usual unchecked execution of Cancels and
Supersedes on our server, and implemented methods that honor only
Cancels and Supersedes from trusted and/or verifiable sources.

We created a whitelist of senders that contains well-known Despammers
("professional" Spam Cancellers) so that we can honor their desirable
Spam Cancels and NoCeM Notices as well as senders of periodic Usenet
postings like FAQs so that they can overwrite older versions of their
texts by Supersedes.

Furthermore, we activated the "Cancel Lock" (aka "canlock")
verification system on our server. Our server does now honor the
article headers "Cancel-Lock:" and "Cancel-Key:" that create a
verifiable connection between an article and a corresponding
Cancel/Supersedes. Users that add Cancel-Lock to their articles and
Cancel-Key to their Cancels/Supersedes can still remove and overwrite
articles on our server. For our own users, our server automatically
creates Cancel-Lock at posting time; a Cancel-Lock already present at
posting time (added by the user himself) will be extended according to
the technical specifications of the system. Analogously, Cancels and
Supersedes through our server will automatically get the corresponding
Cancel-Key after verification and will be executed.

As a result of the new Cancel/Supersedes processing rules, our users
may start seeing several instances of the same article on our server,
or may see articles that do not exist elsewhere (anymore) - our server
will not execute Cancel/Supersedes that are not covered by our
whitelist or secured by canlock because we cannot verify the
legitimacy of the Cancel/Supersedes otherwise.

Our recommendations for all members of Usenet:

    * Regular Users
          o Do not send Cancels, send Supersedes instead. On servers
            that do not execute Cancels/Supersedes (like ours),
            Supersedes will cause a second article to appear near your
            first article so that other readers will see that there is
            a second, newer version of your article.

          o If your newsreading software supports the Cancel Lock
            feature, please activate it. Cancel Lock creates a
            verifiable connection between an article and a corresponding
            Cancel or Supersedes, resulting in a trusted Cancel/Supersedes
            that will be executed. As an added bonus, this system does
            not allow profiling like e.g. PGP signatures do.

    * Senders of periodic Usenet postings (e.g. FAQs) with "Supersedes:"
      header
          o Supply your article with an "Expires:" header.

          o Supply your article with "Cancel-Lock:" and "Cancel-Key:"
            headers.

          o Sign your article's header with PGP ("X-PGP-Sig:").

    * Despammer
          o Sign your Cancels with a suitable cryptographic signature

          o and/or send cryptographic signed NoCeM Notices. The server
            honors NoCeMs (most despammers are already in our whitelist;
            if you think you are missing, please drop us a note at
            n...@individual.net, we will add you after verification).

We apologize for any inconvenience our changes might cause, but we are
confident that diversifying the processing of Cancels and Supersedes
will be a strong change for the better. And we would be glad if other
servers decide to change their processing as well - so sustained
improvement for Usenet at large can be achieved.

Best regards,
NetNews Team Individual.NET