{"id":"https://openalex.org/W7159789960","doi":"https://doi.org/10.3390/info17050426","title":"A Comparative Study of Unsupervised Machine Learning and Deep Learning Techniques for Anomaly Detection in Recommender Systems","display_name":"A Comparative Study of Unsupervised Machine Learning and Deep Learning Techniques for Anomaly Detection in Recommender Systems","publication_year":2026,"publication_date":"2026-04-29","ids":{"openalex":"https://openalex.org/W7159789960","doi":"https://doi.org/10.3390/info17050426"},"language":"en","primary_location":{"id":"doi:10.3390/info17050426","is_oa":true,"landing_page_url":"https://doi.org/10.3390/info17050426","pdf_url":"https://www.mdpi.com/2078-2489/17/5/426/pdf?version=1777459804","source":{"id":"https://openalex.org/S4210219776","display_name":"Information","issn_l":"2078-2489","issn":["2078-2489"],"is_oa":true,"is_in_doaj":true,"is_core":true,"host_organization":"https://openalex.org/P4310310987","host_organization_name":"Multidisciplinary Digital Publishing Institute","host_organization_lineage":["https://openalex.org/P4310310987"],"host_organization_lineage_names":["Multidisciplinary Digital Publishing Institute"],"type":"journal"},"license":"cc-by","license_id":"https://openalex.org/licenses/cc-by","version":"publishedVersion","is_accepted":true,"is_published":true,"raw_source_name":"Information","raw_type":"journal-article"},"type":"article","indexed_in":["crossref","doaj"],"open_access":{"is_oa":true,"oa_status":"gold","oa_url":"https://www.mdpi.com/2078-2489/17/5/426/pdf?version=1777459804","any_repository_has_fulltext":true},"authorships":[{"author_position":"first","author":{"id":"https://openalex.org/A5067034743","display_name":"Rodolfo Bojorque","orcid":null},"institutions":[{"id":"https://openalex.org/I3132940433","display_name":"Politecnica Salesiana University","ror":"https://ror.org/00f11af73","country_code":"EC","type":"education","lineage":["https://openalex.org/I3132940433"]}],"countries":["EC"],"is_corresponding":true,"raw_author_name":"Rodolfo Bojorque","raw_affiliation_strings":["Advanced Computing and Data Research Group, Universidad Polit\u00e9cnica Salesiana, Cuenca 010102, Ecuador","Campus El Vecino, Universidad Polit\u00e9cnica Salesiana, Cuenca 010102, Ecuador","Math Innovation Group, Universidad Polit\u00e9cnica Salesiana, Cuenca 010102, Ecuador"],"raw_orcid":"https://orcid.org/0000-0002-6045-8692","affiliations":[{"raw_affiliation_string":"Advanced Computing and Data Research Group, Universidad Polit\u00e9cnica Salesiana, Cuenca 010102, Ecuador","institution_ids":["https://openalex.org/I3132940433"]},{"raw_affiliation_string":"Campus El Vecino, Universidad Polit\u00e9cnica Salesiana, Cuenca 010102, Ecuador","institution_ids":["https://openalex.org/I3132940433"]},{"raw_affiliation_string":"Math Innovation Group, Universidad Polit\u00e9cnica Salesiana, Cuenca 010102, Ecuador","institution_ids":["https://openalex.org/I3132940433"]}]},{"author_position":"middle","author":{"id":"https://openalex.org/A5006425880","display_name":"Remigio Hurtado","orcid":"https://orcid.org/0000-0001-7472-9417"},"institutions":[{"id":"https://openalex.org/I3132940433","display_name":"Politecnica Salesiana University","ror":"https://ror.org/00f11af73","country_code":"EC","type":"education","lineage":["https://openalex.org/I3132940433"]}],"countries":["EC"],"is_corresponding":false,"raw_author_name":"Remigio Hurtado","raw_affiliation_strings":["Campus El Vecino, Universidad Polit\u00e9cnica Salesiana, Cuenca 010102, Ecuador"],"raw_orcid":"https://orcid.org/0000-0001-7472-9417","affiliations":[{"raw_affiliation_string":"Campus El Vecino, Universidad Polit\u00e9cnica Salesiana, Cuenca 010102, Ecuador","institution_ids":["https://openalex.org/I3132940433"]}]},{"author_position":"middle","author":{"id":"https://openalex.org/A5125923963","display_name":"Miguel Arcos-Argudo","orcid":null},"institutions":[{"id":"https://openalex.org/I3132940433","display_name":"Politecnica Salesiana University","ror":"https://ror.org/00f11af73","country_code":"EC","type":"education","lineage":["https://openalex.org/I3132940433"]}],"countries":["EC"],"is_corresponding":false,"raw_author_name":"Miguel Arcos-Argudo","raw_affiliation_strings":["Advanced Computing and Data Research Group, Universidad Polit\u00e9cnica Salesiana, Cuenca 010102, Ecuador","Campus El Vecino, Universidad Polit\u00e9cnica Salesiana, Cuenca 010102, Ecuador","Math Innovation Group, Universidad Polit\u00e9cnica Salesiana, Cuenca 010102, Ecuador"],"raw_orcid":"https://orcid.org/0000-0002-7056-8588","affiliations":[{"raw_affiliation_string":"Advanced Computing and Data Research Group, Universidad Polit\u00e9cnica Salesiana, Cuenca 010102, Ecuador","institution_ids":["https://openalex.org/I3132940433"]},{"raw_affiliation_string":"Campus El Vecino, Universidad Polit\u00e9cnica Salesiana, Cuenca 010102, Ecuador","institution_ids":["https://openalex.org/I3132940433"]},{"raw_affiliation_string":"Math Innovation Group, Universidad Polit\u00e9cnica Salesiana, Cuenca 010102, Ecuador","institution_ids":["https://openalex.org/I3132940433"]}]},{"author_position":"last","author":{"id":"https://openalex.org/A5125970765","display_name":"Mauricio Ortiz","orcid":null},"institutions":[{"id":"https://openalex.org/I3132940433","display_name":"Politecnica Salesiana University","ror":"https://ror.org/00f11af73","country_code":"EC","type":"education","lineage":["https://openalex.org/I3132940433"]}],"countries":["EC"],"is_corresponding":false,"raw_author_name":"Mauricio Ortiz","raw_affiliation_strings":["Campus El Vecino, Universidad Polit\u00e9cnica Salesiana, Cuenca 010102, Ecuador"],"raw_orcid":"https://orcid.org/0000-0002-5324-0759","affiliations":[{"raw_affiliation_string":"Campus El Vecino, Universidad Polit\u00e9cnica Salesiana, Cuenca 010102, Ecuador","institution_ids":["https://openalex.org/I3132940433"]}]}],"institutions":[],"countries_distinct_count":1,"institutions_distinct_count":4,"corresponding_author_ids":["https://openalex.org/A5067034743"],"corresponding_institution_ids":["https://openalex.org/I3132940433"],"apc_list":{"value":1400,"currency":"CHF","value_usd":1515},"apc_paid":{"value":1400,"currency":"CHF","value_usd":1515},"fwci":0.0,"has_fulltext":true,"cited_by_count":0,"citation_normalized_percentile":{"value":0.61311339,"is_in_top_1_percent":false,"is_in_top_10_percent":false},"cited_by_percentile_year":null,"biblio":{"volume":"17","issue":"5","first_page":"426","last_page":"426"},"is_retracted":false,"is_paratext":false,"is_xpac":false,"primary_topic":{"id":"https://openalex.org/T11512","display_name":"Anomaly Detection Techniques and Applications","score":0.310699999332428,"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"}},"topics":[{"id":"https://openalex.org/T11512","display_name":"Anomaly Detection Techniques and Applications","score":0.310699999332428,"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"}},{"id":"https://openalex.org/T12026","display_name":"Explainable Artificial Intelligence (XAI)","score":0.08969999849796295,"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"}},{"id":"https://openalex.org/T10203","display_name":"Recommender Systems and Techniques","score":0.07370000332593918,"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"}}],"keywords":[{"id":"https://openalex.org/keywords/movielens","display_name":"MovieLens","score":0.7670000195503235},{"id":"https://openalex.org/keywords/recommender-system","display_name":"Recommender system","score":0.7217000126838684},{"id":"https://openalex.org/keywords/anomaly-detection","display_name":"Anomaly detection","score":0.6459000110626221},{"id":"https://openalex.org/keywords/ranking","display_name":"Ranking (information retrieval)","score":0.6215000152587891},{"id":"https://openalex.org/keywords/unsupervised-learning","display_name":"Unsupervised learning","score":0.5874000191688538},{"id":"https://openalex.org/keywords/deep-learning","display_name":"Deep learning","score":0.5490999817848206},{"id":"https://openalex.org/keywords/stability","display_name":"Stability (learning theory)","score":0.546500027179718},{"id":"https://openalex.org/keywords/support-vector-machine","display_name":"Support vector machine","score":0.4885999858379364},{"id":"https://openalex.org/keywords/construct","display_name":"Construct (python library)","score":0.47780001163482666}],"concepts":[{"id":"https://openalex.org/C154945302","wikidata":"https://www.wikidata.org/wiki/Q11660","display_name":"Artificial intelligence","level":1,"score":0.8055999875068665},{"id":"https://openalex.org/C2776156558","wikidata":"https://www.wikidata.org/wiki/Q4353746","display_name":"MovieLens","level":4,"score":0.7670000195503235},{"id":"https://openalex.org/C119857082","wikidata":"https://www.wikidata.org/wiki/Q2539","display_name":"Machine learning","level":1,"score":0.7537999749183655},{"id":"https://openalex.org/C41008148","wikidata":"https://www.wikidata.org/wiki/Q21198","display_name":"Computer science","level":0,"score":0.7498999834060669},{"id":"https://openalex.org/C557471498","wikidata":"https://www.wikidata.org/wiki/Q554950","display_name":"Recommender system","level":2,"score":0.7217000126838684},{"id":"https://openalex.org/C739882","wikidata":"https://www.wikidata.org/wiki/Q3560506","display_name":"Anomaly detection","level":2,"score":0.6459000110626221},{"id":"https://openalex.org/C189430467","wikidata":"https://www.wikidata.org/wiki/Q7293293","display_name":"Ranking (information retrieval)","level":2,"score":0.6215000152587891},{"id":"https://openalex.org/C8038995","wikidata":"https://www.wikidata.org/wiki/Q1152135","display_name":"Unsupervised learning","level":2,"score":0.5874000191688538},{"id":"https://openalex.org/C108583219","wikidata":"https://www.wikidata.org/wiki/Q197536","display_name":"Deep learning","level":2,"score":0.5490999817848206},{"id":"https://openalex.org/C112972136","wikidata":"https://www.wikidata.org/wiki/Q7595718","display_name":"Stability (learning theory)","level":2,"score":0.546500027179718},{"id":"https://openalex.org/C12267149","wikidata":"https://www.wikidata.org/wiki/Q282453","display_name":"Support vector machine","level":2,"score":0.4885999858379364},{"id":"https://openalex.org/C2780801425","wikidata":"https://www.wikidata.org/wiki/Q5164392","display_name":"Construct (python library)","level":2,"score":0.47780001163482666},{"id":"https://openalex.org/C59404180","wikidata":"https://www.wikidata.org/wiki/Q17013334","display_name":"Feature learning","level":2,"score":0.4388999938964844},{"id":"https://openalex.org/C2781067378","wikidata":"https://www.wikidata.org/wiki/Q17027399","display_name":"Interpretability","level":2,"score":0.4268999993801117},{"id":"https://openalex.org/C2776359362","wikidata":"https://www.wikidata.org/wiki/Q2145286","display_name":"Representation (politics)","level":3,"score":0.3677000105381012},{"id":"https://openalex.org/C37736160","wikidata":"https://www.wikidata.org/wiki/Q1801315","display_name":"Adversarial system","level":2,"score":0.35679998993873596},{"id":"https://openalex.org/C50644808","wikidata":"https://www.wikidata.org/wiki/Q192776","display_name":"Artificial neural network","level":2,"score":0.3522000014781952},{"id":"https://openalex.org/C52622490","wikidata":"https://www.wikidata.org/wiki/Q1026626","display_name":"Feature extraction","level":2,"score":0.33649998903274536},{"id":"https://openalex.org/C2778755073","wikidata":"https://www.wikidata.org/wiki/Q10858537","display_name":"Scale (ratio)","level":2,"score":0.31220000982284546},{"id":"https://openalex.org/C124101348","wikidata":"https://www.wikidata.org/wiki/Q172491","display_name":"Data mining","level":1,"score":0.30820000171661377},{"id":"https://openalex.org/C2776401178","wikidata":"https://www.wikidata.org/wiki/Q12050496","display_name":"Feature (linguistics)","level":2,"score":0.29809999465942383},{"id":"https://openalex.org/C2778403875","wikidata":"https://www.wikidata.org/wiki/Q20312394","display_name":"Adversarial machine learning","level":3,"score":0.273499995470047},{"id":"https://openalex.org/C774472","wikidata":"https://www.wikidata.org/wiki/Q6760393","display_name":"Margin (machine learning)","level":2,"score":0.2728999853134155},{"id":"https://openalex.org/C21569690","wikidata":"https://www.wikidata.org/wiki/Q94702","display_name":"Collaborative filtering","level":3,"score":0.27079999446868896},{"id":"https://openalex.org/C2775941552","wikidata":"https://www.wikidata.org/wiki/Q25212305","display_name":"Isolation (microbiology)","level":2,"score":0.26649999618530273},{"id":"https://openalex.org/C67186912","wikidata":"https://www.wikidata.org/wiki/Q367664","display_name":"Data modeling","level":2,"score":0.260699987411499},{"id":"https://openalex.org/C153180895","wikidata":"https://www.wikidata.org/wiki/Q7148389","display_name":"Pattern recognition (psychology)","level":2,"score":0.25459998846054077}],"mesh":[],"locations_count":2,"locations":[{"id":"doi:10.3390/info17050426","is_oa":true,"landing_page_url":"https://doi.org/10.3390/info17050426","pdf_url":"https://www.mdpi.com/2078-2489/17/5/426/pdf?version=1777459804","source":{"id":"https://openalex.org/S4210219776","display_name":"Information","issn_l":"2078-2489","issn":["2078-2489"],"is_oa":true,"is_in_doaj":true,"is_core":true,"host_organization":"https://openalex.org/P4310310987","host_organization_name":"Multidisciplinary Digital Publishing Institute","host_organization_lineage":["https://openalex.org/P4310310987"],"host_organization_lineage_names":["Multidisciplinary Digital Publishing Institute"],"type":"journal"},"license":"cc-by","license_id":"https://openalex.org/licenses/cc-by","version":"publishedVersion","is_accepted":true,"is_published":true,"raw_source_name":"Information","raw_type":"journal-article"},{"id":"pmh:oai:doaj.org/article:1142dea4a5ca4e28a21049ac9d2edd13","is_oa":true,"landing_page_url":"https://doaj.org/article/1142dea4a5ca4e28a21049ac9d2edd13","pdf_url":null,"source":{"id":"https://openalex.org/S4306401280","display_name":"DOAJ (DOAJ: Directory of Open Access Journals)","issn_l":null,"issn":null,"is_oa":false,"is_in_doaj":false,"is_core":false,"host_organization":null,"host_organization_name":null,"host_organization_lineage":[],"host_organization_lineage_names":[],"type":"repository"},"license":"cc-by-sa","license_id":"https://openalex.org/licenses/cc-by-sa","version":"submittedVersion","is_accepted":false,"is_published":false,"raw_source_name":"Information, Vol 17, Iss 5, p 426 (2026)","raw_type":"article"}],"best_oa_location":{"id":"doi:10.3390/info17050426","is_oa":true,"landing_page_url":"https://doi.org/10.3390/info17050426","pdf_url":"https://www.mdpi.com/2078-2489/17/5/426/pdf?version=1777459804","source":{"id":"https://openalex.org/S4210219776","display_name":"Information","issn_l":"2078-2489","issn":["2078-2489"],"is_oa":true,"is_in_doaj":true,"is_core":true,"host_organization":"https://openalex.org/P4310310987","host_organization_name":"Multidisciplinary Digital Publishing Institute","host_organization_lineage":["https://openalex.org/P4310310987"],"host_organization_lineage_names":["Multidisciplinary Digital Publishing Institute"],"type":"journal"},"license":"cc-by","license_id":"https://openalex.org/licenses/cc-by","version":"publishedVersion","is_accepted":true,"is_published":true,"raw_source_name":"Information","raw_type":"journal-article"},"sustainable_development_goals":[],"awards":[],"funders":[],"has_content":{"grobid_xml":true,"pdf":true},"content_urls":{"pdf":"https://content.openalex.org/works/W7159789960.pdf","grobid_xml":"https://content.openalex.org/works/W7159789960.grobid-xml"},"referenced_works_count":16,"referenced_works":["https://openalex.org/W1977290284","https://openalex.org/W1989279326","https://openalex.org/W2029424893","https://openalex.org/W2054141820","https://openalex.org/W2072651985","https://openalex.org/W2100495367","https://openalex.org/W2122646361","https://openalex.org/W2132870739","https://openalex.org/W2219888463","https://openalex.org/W2282861635","https://openalex.org/W2296719434","https://openalex.org/W2908054697","https://openalex.org/W3081229243","https://openalex.org/W3182668916","https://openalex.org/W4241492760","https://openalex.org/W4408977758"],"related_works":[],"abstract_inverted_index":{"Recommender":[0],"systems":[1],"are":[2,26,84,131],"increasingly":[3],"exposed":[4],"to":[5,133,154],"anomalous":[6,150],"user":[7,173],"behavior":[8],"that":[9,143,178],"can":[10],"distort":[11],"recommendation":[12],"outcomes":[13],"and":[14,47,72,92,120,164,185],"compromise":[15],"system":[16,192],"reliability.":[17],"In":[18,123],"real-world":[19],"settings,":[20],"explicit":[21,77],"labels":[22],"identifying":[23,170],"malicious":[24],"activity":[25],"rarely":[27],"available,":[28],"motivating":[29],"the":[30,58,99],"adoption":[31],"of":[32,43,101,149],"unsupervised":[33,81,180],"detection":[34,53,82,135,181],"approaches.":[35],"This":[36],"study":[37],"presents":[38],"a":[39,64,108,166,183],"systematic":[40],"comparative":[41],"analysis":[42],"classical":[44],"machine":[45],"learning":[46,49],"deep":[48],"techniques":[50],"for":[51,169,190],"anomaly":[52],"in":[54],"recommender":[55,191],"systems.":[56],"Using":[57],"MovieLens":[59],"1M":[60],"dataset,":[61],"we":[62],"construct":[63],"user-level":[65],"behavioral":[66],"representation":[67],"based":[68],"on":[69],"statistical,":[70],"temporal,":[71],"interaction-based":[73],"features":[74],"derived":[75],"from":[76],"rating":[78],"data.":[79],"Three":[80],"models":[83,145],"evaluated:":[85],"Isolation":[86],"Forest,":[87],"One-Class":[88],"Support":[89],"Vector":[90],"Machine,":[91],"an":[93],"autoencoder-based":[94],"neural":[95],"network.":[96],"To":[97],"address":[98],"absence":[100],"ground-truth":[102],"labels,":[103],"evaluation":[104],"is":[105],"conducted":[106,132],"using":[107],"comprehensive":[109],"label-free":[110],"protocol,":[111],"including":[112],"score":[113],"distribution":[114],"analysis,":[115],"percentile-based":[116],"thresholding,":[117],"ranking":[118,162],"stability,":[119],"inter-model":[121],"agreement.":[122,156],"addition,":[124],"controlled":[125],"experiments":[126],"with":[127],"synthetic":[128],"attack":[129],"profiles":[130],"assess":[134],"performance":[136],"under":[137,194],"different":[138],"adversarial":[139],"strategies.":[140],"Results":[141],"indicate":[142],"individual":[144],"capture":[146],"complementary":[147],"aspects":[148],"behavior,":[151],"exhibiting":[152],"low":[153],"moderate":[155],"An":[157],"ensemble":[158],"scoring":[159],"strategy":[160],"improves":[161],"stability":[163],"provides":[165],"consistent":[167],"mechanism":[168],"highly":[171],"deviant":[172],"profiles.":[174],"The":[175],"findings":[176],"suggest":[177],"ensemble-based":[179],"constitutes":[182],"practical":[184],"interpretable":[186],"first-layer":[187],"screening":[188],"approach":[189],"monitoring":[193],"label-scarce":[195],"conditions.":[196]},"counts_by_year":[],"updated_date":"2026-06-19T15:47:20.252518","created_date":"2026-05-03T00:00:00"}
