One of the great things about using WordPress is that you can add "plug-ins" which are programs that add functionality to your wordpress blog/site. There are 1000's of different wordpress plug ins and they are free and usually very easy to install and setup.
You can goto the WordPress plugin directory to find all the different plugins that are available.
One of the first plugins you should have is the Akismet anti spam plugin.
Akismet checks your comments against the Akismet web service to see if they look like spam or not and lets you
review the spam it catches under your blog's "Comments" admin screen.
This plugin really works great once installed because it captures all the spammer comments and if you don't have this in place, you will get bombarded with spammer comments that you will have to weed through in order to get to the regular non spam comments.
You'll need a WordPress.com API key to use it.