WordPress websites and blogs are frequent targets of spam comments. Notice that these spammers always do not use their real name and leave a backlink to a site, which in most cases may not be related to your website. To effectively stop the link spammers it is better to remove the “Website” or “URL” field from the WordPress comment section.
comment_form_default_fields filter (See codex here), it’s just a matter of a couple line of codes. Put this in your
Now check your comment form and the the URL field should have been removed.