SPAM - Unsolicited Submissions
SPAM is a problem that impacts all publicly accessible forms and fighting is complicated by the fact that spammers and bots are constantly evolving their methods. There are a number of solutions you can use to reduce the amount of spam, but note that there’s not any single anti-spam method in the world able to catch 100% of it.
You can find hundreds of different anti-spam techniques and services, being the most popular ones captcha-based solutions, and the honeypot technique, which we both support and recommend using together. Simply drop reCaptcha or hCatpcha element together with Honeypot element in any form and fulfill the settings. That should considerably reduce the amount, but remember that no solution is definitive.