Akismet is a full-featured spam protection service that uses machine learning and AI technology to assess content people submit to your site in real time. It's got 99.99% accuracy, automates spam filtering so you don't have to, and removes security hassles that can slow people down. Akismet works on lots of different platforms and offers several API choices, and there are various pricing tiers depending on your needs.
Another serious option is Verisoul, a fraud detection and prevention service that automates manual processes and consolidates vendors. It's designed to thwart a broad range of fraud, including spam and scams, payment fraud and bot accounts. Verisoul offers automated decision-making and lots of integration options, so it's good for a variety of businesses.