WordPress comes standard with the Akismet Plugin that can help you to prevent comment spam on your website.
Comment spam is what some people write into comments just to get links to their own website. You can identify them by their use keywords in the name they use to connect to the URL. And the fact that the comment is either off topic or has just some generic text.
There are a lot of automatic spam comment software programs on the internet and some scammy sites that will offer to get you a lot of backlinks, mostly done by usgin spambots for commenting on related blogs.
To use Akismet you need to register for an API key and Akismet is free so long as it’s for personal, non-commercial use. If you use if for a business or if your site makes a profit by use of advertising options or partner links you need to have a paid license.
If your site is for a business or if it promotes a product or service, you should pick from one of our paid account options
I used Akismet in the past and it served me well on a personal blog, but I still needed to go into the spam comments to clean them out and approve some legitimate comments which where falsly identified as comment spam.
I now use a free plugin that reduced my spam to nearly nothing 
I use the Growmap Anti Spambot Plugin together with the Simple Trackback Validation that will check tracback spam.
You will see a drastic reduction of automatic spam and real commenters don’t have to bother with captcha’s or math fields, they can simply check the option box before the Confirm you are NOT a spammer text.
A real easy implementation as all you need to do is upload and activate the plugin.
