CAPTCHA

What is CAPTCHA?
'Completely automated public Turing test to tell computers and humans apart', better known as CAPTCHA, is a test to ensure answers by a human versus a computer program.

CAPTCHA was developed at Carnegie Mellon University by Nicholas J. Hopper, John Langford, Luis von Ahn, and Manuel Blum. CAPTCHA automatically creates response challenges by providing a problem that can only be solved by humans by automatically preventing access to system software and requesting a series of typed characters.

Ein Computer verwaltet CAPTCHA für einen Menschen, während ein Mensch den Turing test an eine Maschine anwendet.

Websites use CAPTCHA to prevent quality of service (QoS) degradation from bots or other automated programs by using a test that only humans can understand. CAPTCHA increases security through background noise that appears as letters or links to real letters. All online systems are constantly vulnerable to hacking attacks. Brute force hacking attempts can be avoided by including a CAPTCHA element in a registration form. This is only an element of security as it is very easy for a human to bypass a CAPTCHA element on a page.

For the average user, the CAPTCHA element is 'that pesky box at the bottom of a registration form'. While it is easy to implement from a web development perspective, a web designer must decide whether the user annoyance is worth the added security.