How can I Block Spam Comments on WordPress Sites?
In my humble experience, there are techniques built into WordPress that make Spam comments very much a non-issue:
A) Moderate all comments: Admin Dashboard>Settings>Discussion>Before a comment appears>An administrator must always approve the comment
B) To place all comments with (spam) links into spam comments: Admin Dashboard>Settings>Discussion>Comment Moderation>Hold a comment in the queue if it contains> 1 >or more links. (A common characteristic of comment spam is a large number of hyperlinks.)
C) Admin Dashboard>Settings>Discussion>Comment Blacklist> Add to this list:
D) Admin Dashboard>Settings>Discussion>Other comment settings>Automatically close comments on articles older than>14>days
(Leaving comments open for a long time will have the biggest impact on how much spam comments are received)
E) Admin Dashboard>Settings>Discussion>E-mail me whenever>A comment is held for moderation>Comments sent to spam are not emailed.
F) Update the comments form to note that comments are moderated, links not allowed, and language must be about the post/page.
G) Empty the Comment Spam daily (often)>Check all>Delete Permanently.