Breaking Text CAPTCHA by Repeated Information

Jae Hyeon Woo, Moosung Park, Kyungho Lee

Research output: Chapter in Book/Report/Conference proceedingConference contribution


CAPTCHA is a simple challenge-response tool to determine whether the user is a bot or human. The user must answer required text, calculate questions, or choose some images from the provider’s choice. D portal site, which is one of the most famous web portal site in Korea, asks text response in CAPTCHA image when joining a cafe group, but this CAPTCHA is structured in a very regular format which can be read very simply if used repeatedly. We can read the text characters by bot with very high accuracy through some easy steps, among 2,000 sample CAPTHCAs.

Original languageEnglish
Title of host publicationInformation Security Applications - 18th International Conference, WISA 2017, Revised Selected Papers
EditorsBrent ByungHoon Kang, Taesoo Kim
PublisherSpringer Verlag
Number of pages10
ISBN (Print)9783319935621
Publication statusPublished - 2018
Event18th World International Conference on Information Security and Application, WISA 2017 - Jeju Island, Korea, Republic of
Duration: 2017 Aug 242017 Aug 26

Publication series

NameLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
Volume10763 LNCS
ISSN (Print)0302-9743
ISSN (Electronic)1611-3349


Other18th World International Conference on Information Security and Application, WISA 2017
Country/TerritoryKorea, Republic of
CityJeju Island

Bibliographical note

Funding Information:
Acknowledgments. This work was supported by Defense Acquisition Program Administration and Agency for Defense Development under the contract (UD060048AD).


  • Analysis
  • Attack
  • Bot
  • Break
  • Portal
  • Text

ASJC Scopus subject areas

  • Theoretical Computer Science
  • Computer Science(all)


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