block list

A  block list  is a list of accounts that a user has blocked on a service or site.

Why
You should keep a block list so you can automatically reject spam or otherwise abusive webmentions.

How to
dobrado checks a block list when receiving webmentions. It currently confirms with the sender that the webmention was received, but then discards the mention and logs the request as coming from a blocked domain. (It may be more appropriate to tell the sender that they have been blocked?)

IndieWeb Examples
can add domains to a block list on his site:

Flickr
Flickr, on your contacts list page (e.g. https://www.flickr.com/people/tantek/contacts/ - substitute your own username for "tantek") has a link with text "Your Block List" at the bottom left which links to:
 * https://www.flickr.com/people/tantek/contacts/ignore/

Twitter
Twitter shows the accounts you've blocked under settings:
 * https://twitter.com/settings/blocked



Apps with OAuth read permissions on your account can also fetch your blocklist per:
 * https://dev.twitter.com/rest/reference/get/blocks/list

Implementation discussions

 * Bridgy: https://github.com/snarfed/bridgy/issues/473
 * A WebMention Endpoint: https://github.com/voxpelli/webpage-webmentions/issues/31