If you are unfortunate enough to get spammed, you may be pounded by thousands of spam comments. Please consult your own IT professional for advice, but I have found this tip works perfectly. To remove unapproved comments manually could take hours (20 at a time from within WordPress Dashboard/Comments). To remove thousands of comments in seconds, I logged in to my hosting account (cpanel), navigated to “phpMyAdmin”, selected the database from list on left (corresponds to domain username), then chose the “SQL” tab, and added the following:
DELETE FROM wp_comments WHERE comment_approved = '0'
Then hit “Go” to run the SQL query, and spam gone.