You can disable external comment requests for WordPress. The following steps block requests to the wp-comments-post.php file that come from outside your WordPress site, which can help prevent comment SPAM.
RewriteEngine OnRewriteCond %{REQUEST_METHOD} POSTRewriteCond %{REQUEST_URI} .wp-comments-post\.php*RewriteCond %{HTTP_REFERER} !.*yourdomain.com.* [OR]RewriteCond %{HTTP_USER_AGENT} ^$RewriteRule (.*) http://%{REMOTE_ADDR}/$ [R=301,L]
Now it will be more difficult for comment SPAM bots to post on your WordPress pages and posts.