I have tried tens of plugins that address security issues, uncontrolled spam messages, malware and malicious activities... but all of them only worked in part. While all fixed the spam comments problem, for instance, none of them were able to prevent spam messages to be sent through my contact forms.
Having tried several well-known plugins that were rated among the best ones, and being very unhappy with the quantity of spam messages I received on a daily basis, I decided to install WP Cerber Security, Anti-Spam & Malware Scan, and gave it a try: BEST DECISION EVER!!! It got rid of everything, from the spam messages I kept receiving to my inbox, to the security issues and malicious activities. It took less than 10 minutes to customize the settings, and then I was done.
If you are having similar issues, do yourself a favor and install this plugin: you won't regret it!!!