Fortify

You can visit Fortify settings page and enable saving blocked comments as spam in the spam section.
To enabled that you need to go to: WordPress admin dashboard => Settings section => Fortify
Saving blocked comments into spam section is disabled by default.
Saving spam comments can help you to keep all the comments saved and review them in future if needed. You can easily mark comment as “not spam” if some of the comments have been blocked by mistake.

Fortify plugin blocks 100% of automatic spam messages (sent by spam-bots via post requests).
Plugin does not block manual spam (submitted by spammers manually via browser).

• Disqus
• Jetpack Comments
• AJAX Comment Form
• bbPress

The blocking algorithm is based on “honeypot technique” and the fact that spam bots does not have JavaScript enabled.
Fortify plugin adds invisible to regular users input fields.
And spam bots fill in those fields which helps to identify that as spam.

You can find the info block with total spam blocked counter in the admin comments section.
You can hide or show this info block in the “Screen Options” section.
The visibility option for this info block is saved per user.

Plugin blocks spam only in comments form section and does not block spam from any other forms on site.
If you installed and activated the plugin and you still receiving spam – probably this could be because of some other forms on your site (for example feedback form).

Users rarely use trackbacks because it is manual and requires extra input. Spammers uses trackbacks because it is easy to cheat here.
Users use pingbacks very often because they work automatically. Spammers does not use pingbacks because backlinks are checked.
So trackbacks are blocked but pingbacks are enabled.
You may read more about the difference between trackbacks and pingbacks

All modern browsers and IE8+ are supported.

You may check out the source code of the plugin.