One of my most favourite FREE anti-spam plugins is Antispam Bee, found in the WordPress plugin repository. It has a number of settings that help keep the spammers away, along with notification when spam is being caught, either as a dashboard graphic or an email notification. The plugin has a 4.7 star rating and has been downloaded and installed as of this moment, more than 200,000 times. Unfortunately it is incompatible with Disqus, Jetpack comments and Ajax comment sytems, but all else does well. For complete details, https://github.com/pluginkollektiv/antispam-bee/wiki (you may need to use your Google translate function).