The akismet plugin is mandatory in any wordpress installation.
This plugin will protect your blog from spam in comments.
Once installed go to “Plugins >> Akismet configuration” to insert your API key to allow the plugin to start functioning properly.
The API key can be obtained from the Akismet official website and is free for personal and non commercial use.
I fought comment spamming by using the DISQS plugin but you still get spamming via fake backlinks, trackbacks, contact forms.
To prevent SPAM you could look at a few Akismet alternatives.Akismet anti-spam wordpress plugin,