Preventing spam in Wordpress

When Wordpress is not sufficiently protected or monitored, spambots may take advantage and use the blog article comments system to post thousands of messages (needless to say, with links to their shady activities). This has a negative impact on your blog (nobody will leave a serious comment) as well as the server itself, overloading it and impacting other sites in the same environment.

Actions to be carried out

Restrict comments to registered users only
Install an effective Captcha system (e.g. via a plugin)
Add an anti-spam plugin: Askimet / Anti-spam Bee / SI CAPTCHA Anti-Spam etc.
Set up the solution offered by Wordpress codex (click here)
Find out more via a Google search

More information/References

http://codex.wordpress.org/fr:FAQ_Combattre_les_Spams_de_Commentaires