Set time limits for filling out the form
Robots enter data instantly, while humans need some time to type their name whatsapp lead and email address. Using this logic, you can filter out bots as soon as they're filling out the fields.
But it's not that simple: many browsers have an autofill feature for forms. Users don't waste time entering their email address, meaning the script might consider them a bot. Furthermore, most bots can already fill out forms as quickly as humans. So this method can be used as a complement to others, but don't expect it to filter out all bots on its own.
Add a hidden field
The logic is this: a person sees two input fields on a website (name and email). However, there's actually a third field hidden in the code.
The robot scans the website code, not the outer shell, so it sees this field and fills it in. This signals the website's script not to accept data from this user.
This would seem like a foolproof method of protection. But the bot will attempt to submit data through the form in every possible combination: filling in some fields and leaving others blank, alternating their contents, and so on. One way or another, it will figure out the correct way to submit the data and break your protection, so the method is unreliable.
Block user-agent
Spammers use specific user-agent headers (the identifier of a specific user). You can even find lists of spambot user-agents online and block them in advance in your htaccess file. However, keep in mind that this won't completely protect you. Bots can spoof user-agents and successfully bypass these blocking methods.
Set traps
For example, using a hidden link. A human can't see it, but it's in the code. The bot follows this link, and that's when you block its IP. But keep in mind that if you use a trap code found publicly available online, it most likely won't work.
Ideally, write a unique trap yourself, but that requires resources. If you have a skilled specialist who can create such a trap, consider yourself lucky.
Use reCAPTCHA services
Services designed specifically to combat spambots are the best form of protection, provided their creators regularly update the algorithms that block unwanted visitors. Therefore, if you decide to use services, choose the most popular ones from reputable developers.