NoCeM (pronounced "No See 'Em") is a protocol for issuing notices that other Usenet participants can use to identify and filter out spam or other unwanted messages. Notices are authenticated using PGP signing to prevent forgery.

Who can use NoCeM?

End users can filter using NoCeM if they have a newsreader that supports it. Gnus for Emacs is one such newsreader, although unfortunately it has not been widely adopted in other newsreaders. In practice, NoCeM notices are mostly issued and acted upon by server administrators, to filter spam at server level.

Administrators can use NoCeM-on-spool software such as perl-nocem for INN 2.

How can I find out more about NoCeM?

The most up-to-date site is the NoCeM Registry.

There is also some older information at the CancelMoose Home Page.

Where can I discuss NoCeM on Usenet?

The following newsgroups would be good places:

news.admin.net-abuse.usenet	Discussion of methods to control spam and other abuses of Usenet
news.software.nntp	NNTP server software and administration
news.lists.filters	Notices for automated news filtering systems (including NoCeM)
alt.nocem.misc	Discussion of the NoCeM project (also used for publishing NoCeM notices)

Note: there used to be a news.admin.nocem newsgroup, but it was removed in 2011 as part of a reorganisation of the news.* hierarchy.