Adding the Google reCaptcha on forms limits the amount of spam you may be getting, but not all spam can be filtered for several reasons:
- not all attacks are machine-made, people are also paid to send you spam, one form at a time,
- machine attacks are getting 'smart',
- the Google reCaptcha settings are too weak.
Although there is nothing you can do about the spam you receive, you can still check your Google reCaptcha settings and ensure that they are optimized for your situation.
Go to the Google reCaptcha administrator console.
Access the settings.
Go down to the security preferences
section
Set the security to most secure. This will present the challenges to more users, but it will definitely limit more illegitimate ones.