[Foundation-l] guarding a wiki

Sun Apr 17 10:30:05 UTC 2005

Walter van Kalken (walter at vankalken.net) [050417 12:40]:

> >If so, then "soft closing" might be a good solution to explore.  A "soft
> >closed" wiki requires a captcha for posting, disallows external links,
> >implements the 'nofollow' tag, etc.

> Forgive my ignorance as a non geek-english speaking cloggy ........ what 
> is captcha?

    http://en.wikipedia.org/wiki/Captcha

A captcha (an acronym for "completely automated public Turing test to tell
computers and humans apart") is a type of challenge-response test used in
computing to determine whether or not the user is human. The term was
coined in 2000 by Luis von Ahn, Manuel Blum, and Nicholas J. Hopper of
Carnegie Mellon University, and John Langford of IBM. A common type of
captcha requires that the user type the letters of a distorted and/or
obscured sequence of letters or digits that appears on the screen. Because
the test is administered by a computer, in contrast to the standard Turing
test that is administered by a human, a captcha is sometimes described as a
reverse Turing test.

Captchas are used to prevent bots from using various types of computing
services. Applications include preventing bots from taking part in online
polls, registering for free email accounts (which may then be used to send
spam), and, more recently, preventing bot-generated spam by requiring that
the (unrecognized) sender successfully pass a captcha test before the email
message is delivered.

By definition, captchas have the following characteristics:

    * They are completely automated. This avoids the necessity for human
      maintenance or intervention in the test, with obvious benefits in
      cost and reliability.
    * The algorithm used is made public, though it may be encumbered by a
      patent. This is stipulated so as to require that breaking a captcha
      requires the solution of a hard problem in the field of artificial
      intelligence (AI) rather than just the discovery of the (secret)
      algorithm, which could be obtained through reverse engineering or
      other means.

- d.