To protect forms such as contact forms, login pages, or search queries from misuse, you should use a Captcha.
Captcha is a process used to find out whether the action was requested by a person or a machine. The user is asked a question to perform certain actions. Only if this question has been answered correctly will the desired action be performed. An action can be, for example, the sending of contact details in a form, user registration on a web page, or the start of a search inquiry in a forum or Blog.
Captchas can look like this:
How to Secure Your Forms
Do you use a CMS (Content-Management-System) like Joomla, Wordpress or Typo3?
Many CMS manufacturers already offer ready-made plugins that you can install in the administration area of your website. A list of the different Captcha plugins can be found here:
Have you programmed your own website or integrated freely available forms?
Use one of the many free captcha methods that provide PHP libraries and tutorials to make sensitive areas of your website more secure. For this purpose we have compiled a small selection of providers for you: