In WordPress, spam usually comes in the form of comment spam, either as regular comments or as trackbacks. If you run a WordPress site that is listed in search engine results, chances are that comment spam will become something you’ll need to worry about sooner rather than later. Fortunately, there is a wide selection of spam protection plugins that can help you deal with it.
The most popular one is Akismet. It’s developed by Automattic, the company behind WordPress.com, and it comes bundled with every installation of WordPress. Unless you have manually removed it, you should already have it listen in Plugins → Installed Plugins in your administration panel. To activate it, you’ll need an account on WordPress.com.