Sadly, there is another problem with WordPress — SPAM. WordPress sites that are not protected from spam can end up with comments posted automatically by spam bots. These are usually advertisements and will not be helpful to the site in any way. If you would like to activate an anti-spam plugin, WordPress comes with one called Akismet. There are many different anti-spam plugins for WordPress, but this support article will cover configuring Akismet as it is bundled with WordPress.
Before continuing, its worth noting that Akismet is only free for personal, non-commercial sites. You can see their pricing and sign up for an API key at https://akismet.com/signup.
As this is only an example, we'll choose the free version. To do this, click the 'Sign Up' button under the Personal plan section. Slide the slider under the 'What is Akismet worth to you?' question, all the way to the left. The yearly contribution will become $0 which means you'll be signing up for a free account. Fill in the form on the page and then click on the 'Continue' button. It's now time to check your email and retrieve your API key that Akismet have just sent you. Copy your API key to the clipboard.
Now that you have your API key, its time to go and enable Akismet in the WordPress control panel. Go to the 'Installed Plugins' page, and choose the 'Activate' option under the Akismet entry. A notification will be displayed, stating 'Akismet is almost ready. You must enter your Akismet API key for it to work.' Click on the 'enter your Akismet API key' link. Paste your Akismet API key in the blank text box, and then click the 'Update options' button. You should now see the message 'Your key has been verified. Happy blogging!' Your site is now metaphorically bulletproof.