poku

“Block Spam Comment” definitely blocks comments of bots without settings or Captcha.
The three systems of “Block Spam Comment” using JavaScript make it impossible for bots to post comments, because bots cannot use JavaScript. Spam comments are not saved, so it reduces load on your server and save time to delete spam comments.
You can see how many spam comments were blocked and data about IP and user agent of bots. You also can download the csv file with that data.

Block Spam Comment

Block spam comments definitely without settings or Captcha.

Flector

The plugin sends you an email each time a comment goes to the spam folder. The plugin will come in handy in combination with anti-spam plugins like <a href="https://wordpress.org/plugins/antispam-bee/" rel="ugc">Antispam Bee</a>, <a href="https://wordpress.org/plugins/invisible-captcha/" rel="ugc">Invisible Captcha</a> and others that completely filter out comments from bots. It saves you the trouble of having to visit the “Spam” folder and manually check whether any real comments have been marked as spam by mistake.
We don’t recommend installing this plugin if you use <a href="https://wordpress.org/plugins/akismet/" rel="ugc">Akismet</a> only – you’ll be drowned in hundreds of emails every day.
If you liked my plugin, please rate it.

Spam Notifier

The plugin sends an email message when a comment goes to the spam folder.

Block Spam Comment vs Spam Notifier