[bct] Re: Fw: CAPTCHA the Internet

  • From: "Brent Harding" <bharding@xxxxxxxxxx>
  • To: <blindcooltech@xxxxxxxxxxxxx>
  • Date: Mon, 27 Feb 2006 20:03:41 -0600

Yeah, it is really getting ridiculous. I'm going to have to get my money out of 
one of my bank accounts and find a credit card elsewhere some how. I just 
wonder who would give me one, had an advantage at the credit union of having 
money in the savings account. I'm just trying to find who to transfer it away 
to, since their captcha is on every login attempt and I heard this is becoming 
a banking trend.

  ----- Original Message ----- 
  From: Ray Foret Jr. 
  To: blindcooltech@xxxxxxxxxxxxx 
  Sent: Monday, February 27, 2006 6:04 PM
  Subject: [bct] Fw: CAPTCHA the Internet

  ----- Original Message ----- 
  From: Barb O'connor 
  To: broconnor1972@xxxxxxxxxxxxx 
  Sent: Monday, February 27, 2006 2:25 PM
  Subject: CAPTCHA the Internet

  I thought you might find this interesting.


  Tag-strategia.com (Blog)
  Tuesday, February 21, 2006

  CAPTCHA the Internet

  CAPTCHA (an acronym for "Completely Automated Public Turing test to tell
  Computers and Humans Apart") has been on my mind ever since Phil Windley
  suggested a graphical CAPTCHA would make a good web service. I thought there
  might be those willing to pay to use it. Well, it's been done.

  There is a need for this type of test. Yahoo! and Hotmail use a CAPTCHA to
  stave off spammers when a user requests an email account. I suspect the most
  common use is on other sites is an attempt block automated comment spam in

  CAPTCHA excludes legitimate users

  As the W3C points out graphical CAPTCHAs are a significant barrier to
  low-vision and blind users. Those with learning disabilities, such as
  dyslexia, may also be adversely affected. As visual CAPTCHAs become more
  sophisticated, busy, patterned background becomes more of an issue for
  color-blind users.

  The U.S. Census Bureau estimated that in 1997 about 7.7 million Americans
  had difficulty seeing the words and letters in an ordinary newspaper. The
  American Foundation for the blind reported about 5 in 1,000 Americans are
  legally blind, and gives a low estimate of 1.5 million visually impaired
  computer users. That's a fairly significant potential market to ignore.

  Requiring users to interpret a visual CAPTCHA may lead to legal challenges.
  Earlier this month, the National Federation for the Blind filed suit against
  Target, claiming target.com discriminates by not being accessible to
  visually impaired users.


  Some companies are experimenting with audio CAPTCHAs, spelling out random
  letters with random noise in the background. However, aural disabilities are
  more common than visual ones, so the approach isn't really more accessible.
  Speech recognition software is more advanced than character recognition, so
  the purported purpose of differentiating between humans and computers is not
  filled anyway.

  CAPTCHA is broken

  Several projects to crack common visual CAPTCHA algorithms, particularly The
  CAPTCHA Project (by the Carnegie Mellon School of Computer Science), the UC
  Berkeley Computer Vision Group, and Sam Hocevar's PWNtcha, have had good
  success. Howard Yeend demonstrated a vulnerability in several public
  algorithms where he could reuse a solution several thousand times after
  manually solving it once.

  Social engineering is often easier than fancy programming. The first widely
  recognized social engineering solution was "borrowing" CAPTCHAs from target
  sites and showing them at entry points to porn sites. Visitors to porn sites
  would solve the CAPTCHAs, allowing spammers to get essentially free labor.
  Amazon's Mechanical Turk (tagline: "Artificial Artificial Intelligence"),
  which gives micro-payments for simple tasks is an example of another way
  CAPTCHAs could be defeated. Even at a few cents per image, the cost may
  still be too high for spammers, but it is a demonstration that the process
  can be outsourced. After all, the world is flat.

  What is the underlying purpose?

  The real reason for CAPTCHA is to screen undesirables. For low traffic
  sites, it means preventing automated access. This can be accomplished in a
  relatively simple way: add a single required question to the comment submit
  form. Something like "What color was George Washington's white horse?" or
  "Enter the fourth word in this sentence." This is enough to make the form
  non-standard, thus unusable by generic bots. Bypassing this added security
  would be very easy for spammers, the advantage is the relative obscurity of
  most blogs. To target multiple blogs, a spammer would need to address each
  one individually; individual attention is unlikely, so I suggest this method
  is the easiest for bloggers with a knowledge of web programming, and is as
  accessible as a comment form without a CAPTCHA.

  Major sites like Yahoo! and Google have a bigger problem. After all, they
  are targets both because of the value of their services, and their size.
  When it first launched Gmail, Google limited accounts to those who had been
  invited by other active users. Initially there was a good bit of commotion
  in the tech community as gmail.com addresses became a sign of prestige. The
  invitation system allows Google to track which users may be abusing the
  service, and which users invited the abusers. Google has gone a step
  further, and now allows potential users to have an invitation code sent to
  their mobile phones. The number of accounts requested per phone number can
  be tracked. The potential gain from a limited handful of throw-away email
  accounts, and the cost of mobile phones (even disposable ones) is enough to
  deter spammers, because less troublesome alternatives exist.

  If you look at Google's account request page, you'll see a CAPTCHA there.
  Google responsibly offers a way for users with disabilities to bypass the
  CAPTCHA, although it involves human-to-human interaction (and quite a bit
  more time) to complete-a costly alternative.

  Real solutions

  Several solutions to the problems with CAPTCHA have been proposed and
  debated. Most have major cost or accessibility problems.

  It would seem the only good solution is some sort of federated identity
  system, which is really just offloading the trouble of user validation to
  someone else.


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