Question For The Day 06 Dec 06

What are these Images// Technique Known As ??? ( When we Register for a New Mail Account we are normally Asked to type in Manually the Word that is displayed with distortion )
















Hints

1 Purpose :: To distinguish Between Humans and Computers.
2. Trademark by Carnige Mellon Univ.

Answer for the Day 06 Dec 06

CAPTCHA
Completely Automated Public Turing test to tell Computers and Humans Apart