{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"institution":[{"id":[{"id":"https:\/\/ror.org\/03mb6wj31","id-type":"ROR","asserted-by":"publisher"},{"id":"https:\/\/www.isni.org\/000000041937028X","id-type":"ISNI","asserted-by":"publisher"},{"id":"https:\/\/www.wikidata.org\/entity\/Q1640731","id-type":"wikidata","asserted-by":"publisher"}],"name":"Universitat Polit\u00e8cnica de Catalunya","acronym":["UPC"]}],"indexed":{"date-parts":[[2026,7,30]],"date-time":"2026-07-30T18:18:07Z","timestamp":1785435487522,"version":"3.56.0"},"reference-count":0,"publisher":"Universitat Polit\u00e8cnica de Catalunya","license":[{"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"abstract":"<jats:p>Online advertising is consistently considered as the pillar of the \"free\u2022 content on the Web since it is commonly the funding source of websites. Furthermore, the option of delivering personalizad ads has tumed advertising into a really valuable service for users, who receive ads tailored to their interests. Given its success in getting paying customers, online advertising is fueling a billionaire business. The current advertising model builds upon an intricate infrastructure whose main aim is to deliver personalized ads. For this purpose, a wealth of user data is collected, aggregated, processed and traded at an unprecedented rate. However, the intrusiveness and ubiquity of these practices prorrpt serious privacy concems. \r\nIn view of the inherent corrplexity behind the operation of ad platforms, privacy risks in the online advertising ecosystem could be studied from multiple perspectives. Naturally, most of the efforts unveiling these privacy issues concentrate on a specific entity, technology, behavior or context. However, such a segmented approach rright underestimate the benefits of a wider vision of a systerric problem. A lot of privacy protection echanisms have been proposed from the industry and acaderria. The most popular ones resort to radical strategies that hinder the ad distribution process, thus seriously affecting the online advertising ecosystem. Others involve significantly changing the ecosystem, which unfortunately may not be suitable in these times. Consequently, to encourage the adoption of privacy protection in this context, it is fundamental to pose mechanisms that aim at balancing the trade-off between user privacy and the web business model. \r\nFirst, this thesis deals with the need to have a wide perspective of the privacy risks for users within the online advertising ecosystem and the protection approaches available. We survey the online advertising infrastructure and its supporting \r\ntechnologies, and present a thorough overview of the undertying privacy risks and the solutions that may rritigate them. Through a systematic effort, we analyze the threats and potential privacy attackers in this scenario of online advertising.Then, we conduct a corrprehensive survey of the most relevant privacy mechanisms, and classify and con-pare them on the basis of their privacy guarantees and irrpact on the Web. Subsequently, we study the privacy risks derived from real-time bidding, a key enabling technology of modem online advertising. We experimentally explore the potential abuse of the process of user data sharing, necessary to support the auction-based \r\nsystem in online advertising. Accordingly, we propase a system to regula te the distribution of u ser tracking data to potentially interested entities, depending on their previous behavior.This consists in reducing the nurnber of advertising agencies receiving user data. Doing so may affect the ad platform's revenue, thus the proposed system is designed to maxirrize the revenue while the abuse by advertising agencies is prevented to a large degree. Experimentally, the results of evaluation suggest that this system is able to correct rrisbehaving entities, consequently enhancing user privacy. Finally, we analyze the irrpact of online advertising and tracking from the particular perspective of lberoamerica.We study the third-party and ad tracking triggered within local websites in this heterogeneous region not previously studied. We found out that user location in this context would affect privacy since the intensity of third-party traffic, including advertising related flows of information, varies from country to country when local web traffic is simulated, although the total nurnber of entities behind this traffic seems stable. The type of content served by websites is also a parameter affecting the leve! of third-party tracking:publishers assiciated with news shopping categories generate more third-party traffic and such intensity is exarbated for top-world sites<\/jats:p>\n                <jats:p>La publicitat en l\u00ednia t\u00e9 un paper important a Internet que permet finan\u00e7ar habitualment l'operaci\u00f3 de llocs web que ofereixen contingut lliure als usuaris. A m\u00e9s, la personalitzaci\u00f3 dels anuncis ha tornat la publicitat en l\u00ednia un servei valu\u00f3s per als usuaris. Si aconseguirem que hi hagi molts compradors siguin m\u00e9s que possibles, es promour\u00e0 un negoci milionari. El model d'anuncis vigents es basa en una infraestructura completa que lliura els anuncis personalitzats. Pera aix\u00f2, es pot recopilar una gran quantitat de dades d'\u00fas, agregar, processar i vendre molt r\u00e0pidament.  Malauradament, aquestes pr\u00e0ctiques generen riscos de privadesa. Donada la complexitat de l'operaci\u00f3 de les plataformes d'anuncis, els riscos de privacitat es poden estudiar des de diverses perspectives. Naturalment, els esfor\u00e7os per desenvolupar aquests problemes de privacitat es concentren en una entitat, tecnologia, comportament o context espec\u00edfic. Per\u00f2 aquest enfocament subestima els beneficis d'una perspectiva m\u00e9s \u00e0mplia d'un problema integral. Molts mecanismes de protecci\u00f3 han estat proposats des de la ind\u00fastria i l\u2019\u00e0mbit acad\u00e8mic. Els m\u00e9s populars apliquen estrat\u00e8gies radicals que obstrueixen la distribuci\u00f3 d'anuncis, afectant seriosament l\u2019ecosistema d'anuncis. Tamb\u00e9 es pot modificar significativament l\u2019ecosistema, el que no \u00e9s factible per la seva conflictivitat. Aix\u00ed, amb la finalitat de fomentar l'adopci\u00f3 de protecci\u00f3 de privacitat, \u00e9s fonamental plantejar solucions orientades a equilibrar les necessitats de privacitat amb el model de negocis de la web. Inicialment, la tesi ofereix una visi\u00f3 amplia dels riscos de privacitat i els mecanismes de protecci\u00f3 a ecosistema d'anuncis en l\u00ednia. Aix\u00f2 es pot aconseguir basant-se en una revisi\u00f3 de la infraestructura i tecnologies subjacents en aquest context. Analitza sistem\u00e0ticament les amenaces i potencies atacants. A continuaci\u00f3 es revisa exhaustivament els mecanismes de privacitat m\u00e9s rellevants, i es classifica i es compara segons les garanties de privacitat que s'ofereixen i el seu possible impacte a la web. Seguidament, s'estudia els riscos de privadesa derivats de les ofertes en temps real, una tecnologia clau del sistema d'anuncis en l\u00ednia modern. Experimentalment, s'inverteixen els riscos del proc\u00e9s de distribuci\u00f3 de dades d'\u00fas, part del sistema basat en licitacions de la publicitat en l\u00ednia. Es proposa un sistema que regula la distribuci\u00f3 de dades d'\u00fas a tercers, depenent del seu comportament previ. Aix\u00f2 consisteix en reduir el nombre d\u2019ag\u00e8ncies anunciants que rebin dades d'\u00fas. Per mitigar l\u2019impacte sobre els ingressos del sistema d'anuncis, aquesta reducci\u00f3 \u00e9s malaltia i l'objectiu de maximitzar els declaracions ingressades. Experimentalment, es troba que el sistema proposat corregir els comportaments maliciosos, millorant la privacitat dels usuaris. Finalment, s'analitza l'impacte del rastre i la publicitat en l\u00ednia des de la perspectiva iberoamericana. Estudiem el rastreig de tercers i all\u00f2 relacionat amb els anuncis que se generen en llocs web locals en aquesta regi\u00f3 heterog\u00e8nia. Trobem que la ubicaci\u00f3 de l'usuari en aquest context afecta la privacitat de l'usuari ja que aquest rastreig varia de pa\u00eds a pa\u00eds, tot i que el nombre total d'entitats darrere d'aquest transit sembla estable. El tipus de contingut afecta tamb\u00e9 el nivell de rastreig: llocs web de noticies o de compres generen m\u00e9s transit cap a tercers i aquesta intensitat s'exacerba en els llocs m\u00e9s populars.<\/jats:p>","DOI":"10.5821\/dissertation-2117-330390","type":"dissertation","created":{"date-parts":[[2023,9,16]],"date-time":"2023-09-16T01:23:27Z","timestamp":1694827407000},"approved":{"date-parts":[[2020,10,2]]},"source":"Crossref","is-referenced-by-count":1,"title":["Privacy in online advertising platforms"],"prefix":"10.5821","author":[{"given":"Jos\u00e9 Antonio","family":"Estrada Jim\u00e9nez","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"3865","container-title":[],"original-title":[],"contributor":[{"sequence":"additional","affiliation":[],"role":[null]}],"deposited":{"date-parts":[[2026,1,25]],"date-time":"2026-01-25T06:29:29Z","timestamp":1769322569000},"score":1,"resource":{"primary":{"URL":"https:\/\/hdl.handle.net\/2117\/330390"}},"subtitle":[],"editor":[{"given":"Jorge","family":"Forn\u00e9 Mu\u00f1oz","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"editor"}]},{"given":"Javier","family":"Parra Arnau","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"editor"}]}],"short-title":[],"issued":{"date-parts":[[null]]},"references-count":0,"URL":"https:\/\/doi.org\/10.5821\/dissertation-2117-330390","relation":{},"subject":[]}}