Mail Chimp widget – getting spam subscribers

Hello. We are using this plugin to add a mailchimp subscribe form. On the form we only include the email field. This is working and shows sign ups in the mailchimp admin on the list as the source being coming from “API – Generic” with only their email added. However we are getting lots of spam signups which are showing as “API Generic” as their source but are also including their first name in their details even though the form we’ve added doesn’t include a first name field. Is there anything we can do with this plugin to further prevent bots form signing up?