Every blogger faces lot of spamming through commenting. To stop comment spamming we use different method or plugin like Disqus and deafault WordPress plugin Akismet. Another great tricks is to set cookies for comments in WordPress site or blog and you can do this easily by using Cookies for Comments plugin. It sets a cookie on a random URL and check it later when a comment is posted. The comment is marked as spam if the cookie not found.
This plugin inserts a stylesheet or image to site’s html source code. And then a cookie is dropped by the plugin system when a browser loads that inserted stylesheet or image. The comment is only marked as spam if the cookie is missing. The plugin can also mark a comment as spam by examining the time took a user to enter the comment.
First of all get the plugin and install it. Upon installation go to Settings->Cookies for Comments to set necessary parameters: