Who own a blog, forum ore generally a web site handled by a CMS maybe could easily fall into spam.
To limit it there is a very good site that can help, Stop Forum Spam that contains an always updated database by users.
I found very useful the feature for searching by various criteria (IP, username, mail).
Users can report their own spam received compiling a form (a free registration to obtain API key is required)
Very useful also Downloads and Mods & Plugins sections (under Resources). The first allows to read the spam database in offline mode by downloading lists of usernames, e-mail addresses, IPs. The second allows to download plugins for various forum platforms (phpbb, vBulletin, etc…) and CMS (WordPress, Drupal, etc…) and so to protect their site against spammers.
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