Developed Automattic the company WordPress this is one of the popular cloud-based and free anti-spam plugins only developed for WordPress. Akismet employs web service powered by dim servers. The plugin uploads all incoming comments to Akismet's dim servers wherein highly specialist methods are run to evaluate the relevance of the comments. If in Akismet gets need i.e. it can't decide for best whether particular plugin is data or not it moves the comment to the moderation queue.. Akismet is free for personal and non-commercial use with edge of 50 000 comment rechecks year. Similar to Akismet you need to connect to the service using API key and the rest follows... The usage of the plugin is free for up to 5000 daily comment rechecks while the premium one has varying number of pricing. WangGuard also offers excellent add-ons such as MailPoet Connector Blacklisted Words and others.. Even if few insanely lazy bots manage to elude the plugins first line of defense the surface called Algorithmic Anti-Spam Layer uses over detection methods. The plugin adds client-side generated checkbox to WordPress comment box which the users much recheck to confirm that they are not spammer.. According to the plugin's page.. WPBruiser GoodBye Captcha is anti-spam and security plugin is based on methods that identify data bots with any annoying and hard to read captcha images... For example if the plugin reports positive i.e. if it detects valid comment as data then that comment never enters WordPress site and you never get to see it. As WordPress I think the application of picking the center anti-spam WordPress plugin dependent on the categories of the books you're receiving..
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