If you enter the wrong email and password into the login page twice you will see a CAPTCHA. CAPTCHA stands for “Completely Automated Public Turing Test to tell Computers and Humans Apart”. It is used in this case to verify that a person and not an automated program is attempting to login.
CAPTCHA displayed after wrong email and password combination entered]]
You can toggle the CAPTCHA on or off for your entire system by going to Menu icon > Global Settings > Security tab > and choose either enabled or disabled. The inherit choice only affects signup pages and will not disable CAPTCHA on the login.