Captcha is a tool that prevents brute force attacks on the Bamboo login screen. A brute force attack occurs when an attacker uses malicious code to make automated, repeated login attempts on a Bamboo site with the aim of gaining access to that Bamboo site.

A Bamboo system administrator can configure Bamboo to block automated login attempts. Once a certain number of failed login attempts has been reached (the default is three) Bamboo's Captcha feature will be activated. When Captcha is activated, users will need to recognise a distorted picture of a word and must type the word into a text field. This is easy for humans to do, but very difficult for computers.