In reply to Todd Lahman.

I was using Simple Comments several years ago, but then free version became just a front end to pitch commercial plugin version and was not effective anymore...

My winning combination at the moment (I use it over a year now), that I employ on all of my sites, is:

Bad Behavior ( https://wordpress.org/plugins/bad-behavior/ ) that filters 99,99% of bots and the rest of them are sorted out by a free plugin:

Stop Spam Comments ( https://wordpress.org/plugins/stop-spam-comments/ )

If you will find time and register to get http:BL Access Key, then you will be also contributing to worldwide spam database.

BTW pingbacks/trackbacks are disabled at the creation of the site - it was good idea, but became so much abused, that is not really useful any more :(