The reCaptcha for WooCommerce plugin provides an all-in-one captcha for WooCommerce as well as WordPress. The settings allow you to turn the captcha on or off on required places through the site. This plugin is highly built on WooCommerce as well as WordPress standard so that it will not break your site in any way.
The Sucuri Security WordPress plugin is a security suite meant to complement existing website security. It offers its users a set of security features, each designed to have a positive effect on website security.