How do online communities fight spam?

Originally answered Jan 3, 2017

1. Before approving new members, verify their identity and confirm that they have a legitimate interest in the community’s topic.
2. Publish the rules of conduct for the community where they can easily be found.
3. Monitor online discussions for spam, warn any violators, and remove/block any repeat offenders.

From the SIKM Leaders Community:

POLICY

1. Posts should be personal, relevant to KM, and not advertisements or spam.
2. Members should not send messages which are duplicates of those distributed through other channels, or regular blog posts.
3. Instead, post one-time invitations to join or subscribe.

From What’s your community’s culture?

Recommendations

1. Be selective in admitting members, and then trust them to use common sense when they post. If they violate that trust, then intervene as necessary.
2. If someone posts things that are not valued by the community members or which go against the community’s guidelines, contact them privately. If they persist, remove them from the community.