Version 2 (modified by Sam Hocevar, 13 years ago) (diff)

import table of defeated captchas from the original website

PWNtcha - captcha decoder

PWNtcha stands for "Pretend We’re Not a Turing Computer but a Human Antagonist", as well as PWN capTCHAs. This project’s goal is to demonstrate the inefficiency of many captcha implementations.

For an overview on why visual captchas are a bad idea, see Matt May’s excellent presentation, Escape from CAPTCHA, as well as the W3C’s Inaccessibility of Visually-Oriented Anti-Robot Tests working draft.

History

I created PWNtcha in 2004 as a personal research project, but only published my results, not the program itself. Given the number of captcha-breaking software available for sale now, I changed my mind and decided to publish the PWNtcha source code. It can be downloaded from Subversion:

 svn co svn://svn.zoy.org/libcaca/pwntcha/trunk pwntcha

Note that PWNtcha is now lagging 3 years behind captcha technology and is therefore no longer a very interesting piece of software.

Defeated captchas

PWNtcha is able to detect and decode the following captchas:

Origin Samples PWNtcha efficiency Comments
Authimage source:/pwntcha/testsuite/authimage/authimage_046.jpeg source:/pwntcha/testsuite/authimage/authimage_090.jpeg 100% Vendor site: http://www.gudlyf.com/index.php?p=376
Weaknesses: constant font, aligned glyphs, constant glyph position, constant rotation, no deformation, non-textured background, constant colours, no perturbation.
Clubic source:/pwntcha/testsuite/clubic/clubic_000.png source:/pwntcha/testsuite/clubic/clubic_001.png 100% Weaknesses: constant font, no rotation, no deformation, aligned glyph, constant background, weak colour variation, weak perturbation.
linuxfr.org source:/pwntcha/testsuite/linuxfr/linuxfr_014.png source:/pwntcha/testsuite/linuxfr/linuxfr_022.png source:/pwntcha/testsuite/linuxfr/linuxfr_081.png 100% Weaknesses: constant font, aligned glyphs, no rotation, no deformation, non-textured background, weak colour variation, weak perturbation.
LiveJournal? source:/pwntcha/testsuite/livejournal/livejournal_003.png source:/pwntcha/testsuite/livejournal/livejournal_015.png 99% Weaknesses: constant font, constant character position.
lmt.lv source:/pwntcha/testsuite/lmt/lmt_000.png source:/pwntcha/testsuite/lmt/lmt_001.png source:/pwntcha/testsuite/lmt/lmt_002.png 98% Weaknesses: constant font, almost aligned glyphs, no rotation, no deformation, constant background, no colour variation, weak perturbation.
Ourcolony source:/pwntcha/testsuite/ourcolony/ourcolony_001.gif source:/pwntcha/testsuite/ourcolony/ourcolony_002.gif 100% Weaknesses: constant font, no rotation, no deformation, no colour variation, no perturbation.
Paypal source:/pwntcha/testsuite/paypal/paypal_000.jpeg source:/pwntcha/testsuite/paypal/paypal_001.jpeg 88% Weaknesses: constant font, almost aligned glyphs, no rotation, no deformation, constant background, no colour variation, no additional perturbation.
phpBB source:/pwntcha/testsuite/phpbb/phpbb_015.png 97% Vendor site: http://www.phpbb.com/
Weaknesses: constant font, no rotation, no deformation, constant colours, weak perturbation.
Scode and derivatives source:/pwntcha/testsuite/scode/scode_000.png source:/pwntcha/testsuite/auditor/auditor_022.png source:/pwntcha/testsuite/scode/scode_001.png 100% Vendor site: http://james.seng.cc/archives/000145.html
Weaknesses: at most 3 different fonts, no rotation, no deformation, weak colour variation, useless perturbation (separate colour key).
Slashdot source:/pwntcha/testsuite/slashdot/slashdot_009.jpeg source:/pwntcha/testsuite/slashdot/slashdot_010.jpeg 89% Weaknesses: constant font, no deformation, constant colours, weak perturbation.
vBulletin source:/pwntcha/testsuite/vbulletin/vbulletin_000.jpeg source:/pwntcha/testsuite/vbulletin/vbulletin_001.jpeg 100% Vendor site: http://www.vbulletin.com/
Weaknesses: constant font, fixed glyph position, no rotation, no deformation, almost constant colours, weak perturbation.
Xanga source:/pwntcha/testsuite/xanga2/xanga2_000.jpeg source:/pwntcha/testsuite/xanga2/xanga2_024.jpeg 49% Weaknesses: fixed horizontal glyph position, no rotation, no deformation, constant colours, insufficient perturbation.