{"id":"https://openalex.org/W7219694366","doi":"https://doi.org/10.5281/zenodo.23142212","title":"Recent Developments and Trends in CAPTCHA: A Review","display_name":"Recent Developments and Trends in CAPTCHA: A Review","publication_year":2026,"publication_date":"2026-10-04","ids":{"openalex":"https://openalex.org/W7219694366","doi":"https://doi.org/10.5281/zenodo.23142212"},"language":"en","primary_location":{"id":"doi:10.5281/zenodo.23142212","doi":"https://doi.org/10.5281/zenodo.23142212","is_oa":true,"landing_page_url":"https://doi.org/10.5281/zenodo.23142212","pdf_url":null,"source":{"id":"https://openalex.org/S4306400562","display_name":"Zenodo (CERN European Organization for Nuclear Research)","issn_l":null,"issn":null,"is_oa":true,"is_in_doaj":false,"is_core":false,"listed_in":[],"host_organization":"https://openalex.org/I67311998","host_organization_name":"European Organization for Nuclear Research","host_organization_lineage":["https://openalex.org/I67311998"],"host_organization_lineage_names":[],"type":"repository"},"license":"cc-by","license_id":"https://openalex.org/licenses/cc-by","version":null,"is_accepted":false,"is_published":false,"raw_source_name":null,"raw_type":"JournalArticle"},"volume":null,"type":"article","is_traditional":true,"indexed_in":["datacite"],"open_access":{"is_oa":true,"oa_status":"green","oa_url":"https://doi.org/10.5281/zenodo.23142212","any_repository_has_fulltext":true},"authorships":[{"author_position":"first","author":{"id":"https://openalex.org/A5093298126","display_name":"Pooja Anil Shende","orcid":"https://orcid.org/0009-0000-0021-4904","observed_orcids":["https://orcid.org/0009-0000-0021-4904"]},"institutions":[],"countries":[],"is_corresponding":false,"raw_author_name":"Shende, Pooja","raw_affiliation_strings":["University Institute of Technology, Bhopal"],"raw_orcid":"https://orcid.org/0009-0000-0021-4904","affiliations":[{"raw_affiliation_string":"University Institute of Technology, Bhopal","institution_ids":[]}]},{"author_position":"middle","author":{"id":"https://openalex.org/A5108325934","display_name":"Rajeev Pandey","orcid":null,"observed_orcids":[]},"institutions":[{"id":"https://openalex.org/I196622127","display_name":"Rajiv Gandhi Technical University","ror":"https://ror.org/03xmje391","country_code":"IN","type":"education","lineage":["https://openalex.org/I196622127"]}],"countries":["IN"],"is_corresponding":false,"raw_author_name":"PANDEY, RAJEEV","raw_affiliation_strings":["University Institute of Technology RGPV"],"raw_orcid":"https://orcid.org/0000-0002-1615-5782","affiliations":[{"raw_affiliation_string":"University Institute of Technology RGPV","institution_ids":["https://openalex.org/I196622127"]}]},{"author_position":"last","author":{"id":"https://openalex.org/A5000385283","display_name":"Shikha Agrawal","orcid":"https://orcid.org/0000-0003-3214-786X","observed_orcids":["https://orcid.org/0000-0003-3214-786X"]},"institutions":[{"id":"https://openalex.org/I196622127","display_name":"Rajiv Gandhi Technical University","ror":"https://ror.org/03xmje391","country_code":"IN","type":"education","lineage":["https://openalex.org/I196622127"]}],"countries":["IN"],"is_corresponding":false,"raw_author_name":"Agrawal, Shikha","raw_affiliation_strings":["Rajiv Gandhi Technical University"],"raw_orcid":"https://orcid.org/0000-0003-3214-786X","affiliations":[{"raw_affiliation_string":"Rajiv Gandhi Technical University","institution_ids":["https://openalex.org/I196622127"]}]}],"institutions":[],"countries_distinct_count":1,"institutions_distinct_count":1,"corresponding_author_ids":[],"corresponding_institution_ids":[],"apc_list":null,"apc_paid":null,"fwci":0.0,"has_fulltext":false,"cited_by_count":0,"citation_normalized_percentile":{"value":0.75795701,"is_in_top_1_percent":false,"is_in_top_10_percent":false},"cited_by_percentile_year":null,"biblio":{"volume":null,"issue":null,"first_page":null,"last_page":null},"is_retracted":false,"is_paratext":false,"is_xpac":false,"primary_topic":{"id":"https://openalex.org/T11800","display_name":"User Authentication and Security Systems","score":0.9984999895095825,"subfield":{"id":"https://openalex.org/subfields/1710","display_name":"Information Systems"},"field":{"id":"https://openalex.org/fields/17","display_name":"Computer Science"},"domain":{"id":"https://openalex.org/domains/3","display_name":"Physical Sciences"}},"topics":[{"id":"https://openalex.org/T11800","display_name":"User Authentication and Security Systems","score":0.9984999895095825,"subfield":{"id":"https://openalex.org/subfields/1710","display_name":"Information Systems"},"field":{"id":"https://openalex.org/fields/17","display_name":"Computer Science"},"domain":{"id":"https://openalex.org/domains/3","display_name":"Physical Sciences"}},{"id":"https://openalex.org/T11644","display_name":"Spam and Phishing Detection","score":0.0007999999797903001,"subfield":{"id":"https://openalex.org/subfields/1710","display_name":"Information Systems"},"field":{"id":"https://openalex.org/fields/17","display_name":"Computer Science"},"domain":{"id":"https://openalex.org/domains/3","display_name":"Physical Sciences"}},{"id":"https://openalex.org/T11689","display_name":"Adversarial Robustness in Machine Learning","score":9.999999747378752e-05,"subfield":{"id":"https://openalex.org/subfields/1702","display_name":"Artificial Intelligence"},"field":{"id":"https://openalex.org/fields/17","display_name":"Computer Science"},"domain":{"id":"https://openalex.org/domains/3","display_name":"Physical Sciences"}}],"keywords":[{"id":"https://openalex.org/keywords/captcha","display_name":"CAPTCHA","score":1.0},{"id":"https://openalex.org/keywords/bots","display_name":"bots","score":0.6510000228881836},{"id":"https://openalex.org/keywords/bot-detection","display_name":"bot detection","score":0.6129999756813049},{"id":"https://openalex.org/keywords/image-based-captcha","display_name":"image-based CAPTCHA","score":0.9879999756813049},{"id":"https://openalex.org/keywords/accessibility","display_name":"accessibility","score":0.6930000185966492},{"id":"https://openalex.org/keywords/adversarial-networks","display_name":"adversarial networks","score":0.7609999775886536},{"id":"https://openalex.org/keywords/online-attacks","display_name":"online attacks","score":0.41100001335144043}],"concepts":[{"id":"https://openalex.org/C163339463","wikidata":"https://www.wikidata.org/wiki/Q484598","display_name":"CAPTCHA","level":2,"score":0.9592999815940857},{"id":"https://openalex.org/C41008148","wikidata":"https://www.wikidata.org/wiki/Q21198","display_name":"Computer science","level":0,"score":0.6868000030517578},{"id":"https://openalex.org/C577917","wikidata":"https://www.wikidata.org/wiki/Q189223","display_name":"Turing test","level":2,"score":0.5916000008583069},{"id":"https://openalex.org/C170130773","wikidata":"https://www.wikidata.org/wiki/Q216378","display_name":"Usability","level":2,"score":0.5655999779701233},{"id":"https://openalex.org/C37736160","wikidata":"https://www.wikidata.org/wiki/Q1801315","display_name":"Adversarial system","level":2,"score":0.4830999970436096},{"id":"https://openalex.org/C38652104","wikidata":"https://www.wikidata.org/wiki/Q3510521","display_name":"Computer security","level":1,"score":0.42879998683929443},{"id":"https://openalex.org/C48103436","wikidata":"https://www.wikidata.org/wiki/Q599031","display_name":"State (computer science)","level":2,"score":0.38029998540878296},{"id":"https://openalex.org/C2522767166","wikidata":"https://www.wikidata.org/wiki/Q2374463","display_name":"Data science","level":1,"score":0.37929999828338623},{"id":"https://openalex.org/C28719098","wikidata":"https://www.wikidata.org/wiki/Q44946","display_name":"Point (geometry)","level":2,"score":0.3779999911785126},{"id":"https://openalex.org/C2780615836","wikidata":"https://www.wikidata.org/wiki/Q2471869","display_name":"USable","level":2,"score":0.36169999837875366},{"id":"https://openalex.org/C154945302","wikidata":"https://www.wikidata.org/wiki/Q11660","display_name":"Artificial intelligence","level":1,"score":0.3280999958515167},{"id":"https://openalex.org/C168031717","wikidata":"https://www.wikidata.org/wiki/Q1530280","display_name":"Balance (ability)","level":2,"score":0.3118000030517578},{"id":"https://openalex.org/C107457646","wikidata":"https://www.wikidata.org/wiki/Q207434","display_name":"Human\u2013computer interaction","level":1,"score":0.2919999957084656},{"id":"https://openalex.org/C2779960059","wikidata":"https://www.wikidata.org/wiki/Q7113681","display_name":"Overhead (engineering)","level":2,"score":0.2799000144004822},{"id":"https://openalex.org/C108827166","wikidata":"https://www.wikidata.org/wiki/Q175975","display_name":"Internet privacy","level":1,"score":0.27570000290870667}],"mesh":[],"locations_count":2,"locations":[{"id":"doi:10.5281/zenodo.23142212","doi":"https://doi.org/10.5281/zenodo.23142212","is_oa":true,"landing_page_url":"https://doi.org/10.5281/zenodo.23142212","pdf_url":null,"source":{"id":"https://openalex.org/S4306400562","display_name":"Zenodo (CERN European Organization for Nuclear Research)","issn_l":null,"issn":null,"is_oa":true,"is_in_doaj":false,"is_core":false,"listed_in":[],"host_organization":"https://openalex.org/I67311998","host_organization_name":"European Organization for Nuclear Research","host_organization_lineage":["https://openalex.org/I67311998"],"host_organization_lineage_names":[],"type":"repository"},"license":"cc-by","license_id":"https://openalex.org/licenses/cc-by","version":null,"is_accepted":false,"is_published":false,"raw_source_name":null,"raw_type":"JournalArticle"},{"id":"doi:10.5281/zenodo.23142213","doi":"https://doi.org/10.5281/zenodo.23142213","is_oa":true,"landing_page_url":"https://doi.org/10.5281/zenodo.23142213","pdf_url":null,"source":{"id":"https://openalex.org/S4306400562","display_name":"Zenodo (CERN European Organization for Nuclear Research)","issn_l":null,"issn":null,"is_oa":true,"is_in_doaj":false,"is_core":false,"listed_in":[],"host_organization":"https://openalex.org/I67311998","host_organization_name":"European Organization for Nuclear Research","host_organization_lineage":["https://openalex.org/I67311998"],"host_organization_lineage_names":[],"type":"repository"},"license":"cc-by","license_id":"https://openalex.org/licenses/cc-by","version":null,"is_accepted":false,"is_published":false,"raw_source_name":null,"raw_type":"JournalArticle"}],"best_oa_location":{"id":"doi:10.5281/zenodo.23142212","doi":"https://doi.org/10.5281/zenodo.23142212","is_oa":true,"landing_page_url":"https://doi.org/10.5281/zenodo.23142212","pdf_url":null,"source":{"id":"https://openalex.org/S4306400562","display_name":"Zenodo (CERN European Organization for Nuclear Research)","issn_l":null,"issn":null,"is_oa":true,"is_in_doaj":false,"is_core":false,"listed_in":[],"host_organization":"https://openalex.org/I67311998","host_organization_name":"European Organization for Nuclear Research","host_organization_lineage":["https://openalex.org/I67311998"],"host_organization_lineage_names":[],"type":"repository"},"license":"cc-by","license_id":"https://openalex.org/licenses/cc-by","version":null,"is_accepted":false,"is_published":false,"raw_source_name":null,"raw_type":"JournalArticle"},"sustainable_development_goals":[],"study_designs":[],"awards":[],"funders":[],"has_content":{"grobid_xml":false,"pdf":false},"content_urls":null,"referenced_works_count":0,"referenced_works":[],"related_works":["https://openalex.org/W7127141608","https://openalex.org/W4415264576","https://openalex.org/W4411447414","https://openalex.org/W7168900243","https://openalex.org/W4416549429","https://openalex.org/W4318559699","https://openalex.org/W7124173097","https://openalex.org/W4385015381","https://openalex.org/W2972352121","https://openalex.org/W88332792"],"abstract_inverted_index":{"The":[0,60,87,199],"Completely":[1],"Automated":[2],"Public":[3],"Turing":[4],"test":[5],"to":[6,45,82,94,113,148,193,205],"Tell":[7],"Computers":[8],"and":[9,22,50,69,78,85,98,107,119,133,164,177,196,216],"Humans":[10],"Apart,":[11],"or":[12],"CAPTCHA,":[13],"has":[14,92,142,153],"changed":[15],"significantly":[16],"since":[17],"it":[18,144,152],"was":[19],"first":[20],"developed":[21],"is":[23,204],"now":[24],"a":[25,115,207],"crucial":[26],"line":[27],"of":[28,66,89,130,201,209,213],"defense":[29],"against":[30,183],"automated":[31],"bots.":[32],"This":[33,167],"study":[34],"examines":[35,62,169],"the":[36,51,63,79,127,170,210],"most":[37,171],"recent":[38,90,172,189],"developments":[39,122],"in":[40,159,174],"CAPTCHA":[41,67,74,100,175,215],"design,":[42],"their":[43,76],"ability":[44],"fend":[46],"off":[47],"online":[48],"attacks,":[49],"difficulties":[52],"associated":[53],"with":[54,137],"developing":[55],"artificial":[56],"intelligence":[57],"(AI)":[58],"methods.":[59],"paper":[61,203],"future":[64],"direction":[65],"technology":[68,176],"provides":[70],"insights":[71],"into":[72],"new":[73,156],"types,":[75],"usability,":[77],"best":[80],"way":[81],"balance":[83,116],"security":[84,118,195],"accessibility.":[86],"goal":[88],"advancements":[91,173],"been":[93],"create":[95],"increasingly":[96],"complex":[97],"intuitive":[99],"variants,":[101],"such":[102,125],"as":[103,126],"behavior-based":[104],"gamified":[105],"audio-based":[106],"image-based":[108],"systems.":[109],"In":[110],"an":[111],"attempt":[112],"achieve":[114],"between":[117],"accessibility,":[120],"these":[121],"address":[123],"problems":[124,132],"computational":[128],"overhead":[129],"difficult":[131],"usability":[134],"for":[135,146],"people":[136],"disabilities.":[138],"However,":[139],"because":[140],"AI":[141],"made":[143],"possible":[145],"bots":[147],"circumvent":[149],"conventional":[150],"CAPTCHAs,":[151],"also":[154,187],"created":[155],"difficulties,":[157],"particularly":[158],"domains":[160],"like":[161],"machine":[162],"learning":[163],"adversarial":[165],"networks.":[166],"article":[168],"assesses":[178],"how":[179],"well":[180],"they":[181],"defend":[182],"contemporary":[184],"threats.":[185],"It":[186],"discusses":[188],"research":[190],"that":[191],"aims":[192],"improve":[194],"user":[197],"experience.":[198],"purpose":[200],"this":[202],"give":[206],"summary":[208],"current":[211],"state":[212],"advanced":[214],"point":[217],"out":[218],"its":[219],"flaws.":[220]},"counts_by_year":[],"updated_date":"2026-10-26T11:51:55.731654","created_date":"2026-10-05T00:00:00"}