NoCeM for Usenet

Authenticated, selective abuse notices

What NoCeM Is

NoCeM is a Usenet protocol for distributing cryptographically signed notices about unwanted articles. A notice identifies articles by Message-ID and states why an issuer considers them unwanted. Each server operator independently decides which issuers and notice types to trust.

NoCeM does not impose a global deletion. A verified notice can remove an article from a participating server's local spool, or act as a third-party killfile for a reader. This makes it safer and more selective than unauthenticated third-party cancel messages.

How It Works

  1. An issuer detects spam or another documented form of abuse.
  2. The issuer publishes a signed NoCeM notice, normally in news.lists.filters.
  3. The receiving server verifies the signature with the issuer's public OpenPGP key.
  4. The server applies the notice only when both the issuer and notice type are explicitly allowed by its local policy.
A key identifies a trusted issuer, not a user or a participating server. TCPReset currently trusting two issuer keys does not mean that only three sites use NoCeM. There is no central telemetry that counts every consumer.

NoCeM complements ingestion and posting filters. On TCPReset, Cleanfeed-NG examines incoming feeds, Postfilter-NG is being evaluated for NNTP client submissions, and NoCeM provides authenticated intelligence after an article has propagated.

How to Contribute

1. Operate and observe a consumer

Process notices from a small set of well-documented issuers. Monitor signature failures, matched articles and false positives. Keep private, time-limited cancellation backups for review.

2. Evaluate additional issuers carefully

Read each issuer's policy, obtain its key from an authoritative source and verify the fingerprint independently. Start with narrow notice types such as spam; never import every available key or trust every type automatically.

3. Publish a clear local policy

Document which notices are accepted, what evidence is required, how mistakes are corrected and how the operator can be contacted. Maintain a working abuse address and a practical response target.

4. Develop a prospective issuer in audit mode

A future TCPReset issuer could turn confirmed Cleanfeed-NG or Postfilter-NG findings into signed notices. Begin without publishing: build a reviewed dataset, measure false positives and require manual confirmation for ambiguous cases. A single classifier result is not sufficient evidence.

5. Request external review

Ask experienced operators and existing issuers to review the detection criteria, policy and test notices. Correct the process before requesting trust from other sites.

6. Publish transparently

When the process is mature, publish the issuer policy, public key, independently verifiable fingerprint, notice types and contact information. Post standards-compliant signed notices to news.lists.filters and allow every receiving operator to choose whether to honour them.

References