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PERL-NOCEM(8) InterNetNews Documentation PERL-NOCEM(8)


perl-nocem - A NoCeM-on-spool implementation for INN 2.x




NoCeM, which is pronounced No See 'Em, is a protocol enabling authenticated third-parties to issue notices which can be used to cancel unwanted articles (like spam and articles in moderated newsgroups which were not approved by their moderators). It can also be used by readers as a third-party killfile. It is intended to eventually replace the protocol for third-party cancel messages.

perl-nocem processes third-party, PGP-signed article cancellation notices. It is possible not to honour all NoCeM notices but only those which are sent by people whom you trust (that is to say if you trust the PGP key they use to sign their NoCeM notices). Indeed, it is up to you to decide whether you wish to honour their notices, depending on the criteria they use.

Processing NoCeM notices is easy to set up:

If not already done, install GnuPG, or an equivalent implementation of the OpenPGP standard, to be able to verify the signature of NoCeM notices. It will provide the gpg and gpgv programs. If GnuPG was already installed when INN was configured, then the paths to these programs were taken into account. Otherwise, you have to set the $gpg and $gpgv variables in pathlib/perl/INN/ to the paths to these programs.

All still active NoCeM issuers use rather modern PGP keys accepted by both GnuPG 1.x and 2.x versions. It is no longer needed to explicitly use gpg1 to process NoCeM notices.

Import the keys of the NoCeM issuers you trust in order to check the authenticity of their notices. You can run the following command:

    gpg --no-default-keyring --allow-non-selfsigned-uid \
        --primary-keyring <pathetc>/pgp/ncmring.gpg --no-options \
        --no-permission-warning --batch --import <key-file>
    chmod 644 <pathetc>/pgp/ncmring.gpg

where <pathetc> is the value of the pathetc parameter set in inn.conf and <key-file> the file containing the key(s) to import. The keyring must be located in <pathetc>/pgp/ncmring.gpg; you only have to create the directory <pathetc>/pgp before using gpg (it will automatically generate the ncmring.gpg file) and make sure the news user can read this file, once generated.

The keys of NoCeM issuers can be found in the web site of The NoCeM Registry: <>. You can even download there a unique file which contains all the keys.

Create a nocem.ctl config file in pathetc indicating the NoCeM issuers and notices you want to follow. This permission file contains lines like:,site

This will remove all articles for which the issuer (first part of the line, before the colon ":") has issued NoCeM notices corresponding to the criteria specified after the colon. Usually, you just keep the lines corresponding to the keys previously installed.

You will also find information about that on the web site of The NoCeM Registry. Note that INN is shipped with an up-to-date nocem.ctl file already configured with the current NoCeM issuers. (Only the keys installed at the previous step are not included, so as to leave you the choice of whom to trust, and download the most recent ones, in case they have changed.)

Add to the newsfeeds file an entry like this one in order to feed perl-nocem the NoCeM notices posted to alt.nocem.misc and news.lists.filters, the usual groups where notices are sent:


with the correct path to perl-nocem, located in <pathbin>. Then, run "inncheck" to ensure the syntax of the modified newsfeeds file is correct, and reload it (via "ctlinnd reload newsfeeds 'NoCeM channel feed'").

Note that you should at least carry news.lists.filters on your news server (or other newsgroups where NoCeM notices are sent) if you wish to process them.

Everything should now work. However, do not hesitate to manually test perl-nocem with a NoCeM notice, using:

    grephistory '<Message-ID>' | perl-nocem

Indeed, perl-nocem expects tokens on its standard input, and grephistory can easily give it the token of a known article, thanks to its Message-ID.

When you have verified that everything works, you can eventually turn off regular spam cancels, if you want, not processing any longer cancels containing "cyberspam" in the Path: header (see the refusecybercancels parameter in inn.conf).


The Perl script itself used to process NoCeM notices.
The configuration file which specifies the NoCeM notices to be processed.
The keyring which contains the public keys of trusted NoCeM issuers.


The Subject header field body is not checked for the @@NCM string and there is no check for the presence of the References header field.

The Newsgroups pseudo header field body is not checked, but this can be done in "local_want_cancel_id()".

The Hierarchies: header is ignored.


Copyright 2000 by Miquel van Smoorenburg <>.

Copyright 2001 by Marco d'Itri <>.


gpg(1), gpgv(1), grephistory(1), inn.conf(5), newsfeeds(5), pgp(1).

2022-05-14 INN 2.6.5