This document discusses CAPTCHAs and how they are used to determine if a user is human or a computer program. It provides examples of when CAPTCHAs are commonly used, such as filling out forms, entering chats, or accessing bank accounts online. It also discusses how CAPTCHAs help prevent hackers from overloading servers with automated requests.

1. Claudio Lima
Teacher: Roza M. Zilles Borba
Novo Hamburgo
May, 2011

3. Completely Automated Public Turing test to tell Computers and Humans Apart
A test used in computing to determine if the user is human or a computer program.
Is asked a question that only a human can answer

4. • Filling up a form on the web
• Entering in a chat
• Sending many mails at the same time
• Consulting your bank account on bank’s online systems
• Checking info at the government websites

5. Client  server model
Client
Client
server
Client
Client

6. Receita Federal
SERVER
can process 100
requests in 1 min

7. If a hacker build a software that can send 400 requests in 1 minute
RECEITA
FEDERAL
can process
100 requests
in 1 min

8. RECEITA
FEDERAL
SERVER is
can process
OUT-OF-DATA

9. It means that:
* ther server will not response to requests
* fix it takes time and money
* the website’s reputation is shaken

11. You
server

12. Foram entrevistados 69,7% dos alunos formados entre 2007 e 2010.
Appears this screen CAPTCHA

13. SOURCE
• The Official captcha website. Available at http://www.captcha.net/ Access in May 27
2011.
• What captcha means . Available at http://www.kirps.com/web/main/_blog/all/do-you-
know-what-the-term-captcha-means.shtml Access in May 25 2011
Contact
claudiolima@feevale.br
twitter.com/claudiodelima
claudiodelima.wordpress.com
Presentation available at slideshare.com/claudiodelima