1. مباني امنيت شبكه CAPTCHA)) به نام خدا مدرس: شهرزاد گلستانی Website: www.shgolestani.ir

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5. 5 HTTP does not distinguish between human & machine users. Malicious bots can be anonymous and distributed.

6. 6 CAPTCHA A PROGRAM THAT CAN TELL WHETHER ITS USER IS A HUMAN OR A COMPUTER

7. 7 CAPTCHA A.MOST HUMANS CAN PASS B.CURRENT COMPUTER PROGRAMS CANNOT PASS A PROGRAM THAT CAN GENERATE AND GRADE TESTS THAT:

8. 8 EXAMPLE PICKS RANDOM STRING OF LETTERS oamg RENDERS IT INTO A DISTORTED IMAGE

9. 9 …AND GENERATES A TEST: TYPE THE CHARACTERS THAT APPEAR IN THE IMAGE

10. 10 CAPTCHA C ompletely A utomated P ublic T uring test to tell C omputers & H umans A part

11. 11 QUICKVOTE Which is the best Computer Science Grad School in the US? CMU MIT vote Berkeley StanfordCornell Princeton

12. 12 Protecting website registration. Preventing comment spam in blogs Protecting E-MAIL (Preventing Spam) Preventing BruteForce And Dictionary attacks Protecting Online polls APPLICATIONS

13. EXAMPLES OF CAPTCHAS 13

14. EXAMPLES OF CAPTCHAS 14 General Approaches: Text (ASCII/Unicode) Image Speech Animation 3-D Combinations of all above

15. EXAMPLES OF CAPTCHAS 15 PIX WHAT ARE THESE PICTURES OF?

16. EXAMPLES OF CAPTCHAS 16 PIX WHAT ARE THESE PICTURES OF? THE IMAGES NEED TO BE RANDOMLY DISTORTED

17. EXAMPLES OF CAPTCHAS 17 PIX WHAT ARE THESE PICTURES OF?

18. EXAMPLES OF CAPTCHAS 18 SOUND-BASED CAPTCHA HUMANS ARE BETTER THAN COMPUTERS AT UNDERSTANDING SPOKEN LANGUAGE

19. EXAMPLES OF CAPTCHAS 19 مباني امنيت شبكه – جوانمرد

20. EXAMPLES OF CAPTCHAS 20 مباني امنيت شبكه – جوانمرد

21. EXAMPLES OF CAPTCHAS 21

22. EXAMPLES OF CAPTCHAS 22