= 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, [http://www.w3.org/2004/Talks/0319-csun-m3m/slide1-0.html Escape from CAPTCHA], as well as the W3C’s [http://www.w3.org/TR/turingtest/ 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 || [[Image(source:/pwntcha/testsuite/authimage/authimage_046.jpeg)]] [[Image(source:/pwntcha/testsuite/authimage/authimage_090.jpeg)]] || 100% || Vendor site: http://www.gudlyf.com/index.php?p=376 [[BR]] Weaknesses: constant font, aligned glyphs, constant glyph position, constant rotation, no deformation, non-textured background, constant colours, no perturbation. ||
|| Clubic || [[Image(source:/pwntcha/testsuite/clubic/clubic_000.png)]] [[Image(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 || [[Image(source:/pwntcha/testsuite/linuxfr/linuxfr_014.png)]] [[Image(source:/pwntcha/testsuite/linuxfr/linuxfr_022.png)]] [[Image(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 || [[Image(source:/pwntcha/testsuite/livejournal/livejournal_003.png)]] [[Image(source:/pwntcha/testsuite/livejournal/livejournal_015.png)]] || 99% || Weaknesses: constant font, constant character position. ||
|| lmt.lv || [[Image(source:/pwntcha/testsuite/lmt/lmt_000.png)]] [[Image(source:/pwntcha/testsuite/lmt/lmt_001.png)]] [[Image(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 || [[Image(source:/pwntcha/testsuite/ourcolony/ourcolony_001.gif)]] [[Image(source:/pwntcha/testsuite/ourcolony/ourcolony_002.gif)]] || 100% || Weaknesses: constant font, no rotation, no deformation, no colour variation, no perturbation. ||
|| Paypal || [[Image(source:/pwntcha/testsuite/paypal/paypal_000.jpeg)]] [[Image(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 || [[Image(source:/pwntcha/testsuite/phpbb/phpbb_015.png)]] || 97% || Vendor site: http://www.phpbb.com/ [[BR]] Weaknesses: constant font, no rotation, no deformation, constant colours, weak perturbation. ||
|| Scode and derivatives || [[Image(source:/pwntcha/testsuite/scode/scode_000.png)]] [[Image(source:/pwntcha/testsuite/auditor/auditor_022.png)]] [[Image(source:/pwntcha/testsuite/scode/scode_001.png)]] || 100% || Vendor site: http://james.seng.cc/archives/000145.html [[BR]] Weaknesses: at most 3 different fonts, no rotation, no deformation, weak colour variation, useless perturbation (separate colour key). ||
|| Slashdot || [[Image(source:/pwntcha/testsuite/slashdot/slashdot_009.jpeg)]] [[Image(source:/pwntcha/testsuite/slashdot/slashdot_010.jpeg)]] || 89% || Weaknesses: constant font, no deformation, constant colours, weak perturbation. ||
|| vBulletin || [[Image(source:/pwntcha/testsuite/vbulletin/vbulletin_000.jpeg)]] [[Image(source:/pwntcha/testsuite/vbulletin/vbulletin_001.jpeg)]] || 100% || Vendor site: http://www.vbulletin.com/ [[BR]] Weaknesses: constant font, fixed glyph position, no rotation, no deformation, almost constant colours, weak perturbation. ||
|| Xanga || [[Image(source:/pwntcha/testsuite/xanga2/xanga2_000.jpeg)]] [[Image(source:/pwntcha/testsuite/xanga2/xanga2_024.jpeg)]] || 49% || Weaknesses: fixed horizontal glyph position, no rotation, no deformation, constant colours, insufficient perturbation. ||

== Other captchas and hard captchas ==

These captchas can currently not be defeated by PWNtcha. Note however that this is not an acknowledgement of efficiency; for instance, [http://www.cs.berkeley.edu/~mori/gimpy/gimpy.html EZ-Gimpy can be easily defeated] by other projects. However, the Passport/Yahoo and CFXCaptcha captchas are probably going to last for a long time.

|| Origin || Samples || Comments ||
|| Drupal || [[Image(source:/pwntcha/testsuite/drupal/drupal_024.png)]] [[Image(source:/pwntcha/testsuite/drupal/drupal_025.png)]] [[Image(source:/pwntcha/testsuite/drupal/drupal_089.png)]] || ||
|| Trencaspammers || [[Image(source:/pwntcha/testsuite/trencaspammers/trencaspammers_000.jpeg)]] [[Image(source:/pwntcha/testsuite/trencaspammers/trencaspammers_025.jpeg)]] [[Image(source:/pwntcha/testsuite/trencaspammers/trencaspammers_038.jpeg)]] || ||
|| Xanga (2) || [[Image(source:/pwntcha/testsuite/xanga2/xanga2_000.jpeg)]] [[Image(source:/pwntcha/testsuite/xanga2/xanga2_024.jpeg)]] || ||
|| 20six || [[Image(source:/pwntcha/testsuite/20six/20six_000.jpeg)]] [[Image(source:/pwntcha/testsuite/20six/20six_001.jpeg)]] || Extremely weak captcha, easily removed perturbation. ||
|| Authimage (3) || [[Image(source:/pwntcha/testsuite/authimage3/authimage3_014.png)]] [[Image(source:/pwntcha/testsuite/authimage3/authimage3_074.png)]] || A very good captcha, but not always human-solvable. ||
|| CFXCaptcha || [[Image(source:/pwntcha/testsuite/cfxcaptcha/cfxcaptcha_071.jpeg)]] || A very good captcha. ||
|| Clearscreen || [[Image(source:/pwntcha/testsuite/clearscreen/clearscreen_012.jpeg)]] [[Image(source:/pwntcha/testsuite/clearscreen/clearscreen_053.jpeg)]] || Weak perturbation, but interesting use of non-alphanumeric characters. ||
|| Cwazymail || [[Image(source:/pwntcha/testsuite/cwazymail/cwazymail_006.jpeg)]] [[Image(source:/pwntcha/testsuite/cwazymail/cwazymail_018.jpeg)]] || An excellent idea, but a critically buggy implementation. ||
|| EZ-Gimpy (eg. Yahoo! Briefcase) || [[Image(source:/pwntcha/testsuite/briefcase/briefcase_084.jpeg)]] || Already defeated by [http://www.cs.berkeley.edu/~mori/gimpy/gimpy.html another project]. ||
|| Hoke || [[Image(source:/pwntcha/testsuite/hoke/hoke_000.jpeg)]] [[Image(source:/pwntcha/testsuite/hoke/hoke_005.jpeg)]] || A very weak captcha. ||
|| .Mac || [[Image(source:/pwntcha/testsuite/dotmac/dotmac_018.jpeg)]] || A weak captcha that is not always human-solvable. ||
|| ICQ || [[Image(source:/pwntcha/testsuite/icq/icq_066.jpeg)]] [[Image(source:/pwntcha/testsuite/icq/icq_087.jpeg)]] || A pretty good captcha that uses a wide variety of backgrounds and fonts. ||
|| IMDb || [[Image(source:/pwntcha/testsuite/imdb/imdb_065.jpeg)]] [[Image(source:/pwntcha/testsuite/imdb/imdb_085.jpeg)]] || A very good captcha with a very well thought implementation, but a small dictionary. ||
|| MS MVPS || [[Image(source:/pwntcha/testsuite/msmvps/msmvps_098.jpeg)]] || Already defeated by [http://www.brains-n-brawn.com/default.aspx?vDir=aicaptcha another project]. ||
|| MVN Forum || [[Image(source:/pwntcha/testsuite/mvnforum/mvnforum_011.jpeg)]] || A pretty good captcha that uses a wide variety of backgrounds and fonts. ||
|| Passport || [[Image(source:/pwntcha/testsuite/passport/passport_000.jpeg)]] || A very good captcha, but not always human-solvable. ||
|| Pichan || [[Image(source:/pwntcha/testsuite/pichan/pichan_000.gif)]] [[Image(source:/pwntcha/testsuite/pichan/pichan_001.gif)]] [[Image(source:/pwntcha/testsuite/pichan/pichan_002.gif)]] [[Image(source:/pwntcha/testsuite/pichan/pichan_003.gif)]] || An apparently weak captcha. ||
|| Screenname || [[Image(source:/pwntcha/testsuite/screenname/screenname_005.jpeg)]] [[Image(source:/pwntcha/testsuite/screenname/screenname_054.jpeg)]] || A pretty good captcha that uses a wide variety of backgrounds, fonts and deformations. ||
|| Yahoo!  || [[Image(source:/pwntcha/testsuite/yahoo/yahoo_053.jpeg)]] || A very good captcha, but not always human-solvable. ||

== Links ==

 * [http://www.brains-n-brawn.com/default.aspx?vDir=aicaptcha Using AI to beat CAPTCHA and post comment spam]
 * [http://www.cs.berkeley.edu/~mori/gimpy/gimpy.html Breaking a Visual CAPTCHA]

Page maintained by [http://sam.zoy.org/ Sam Hocevar]. Contact me for more information: [mailto:sam@zoy.org].