TY - GEN A1 - Vallina, Pelayo A1 - Le Pochat, Victor A1 - Feal, Álvaro A1 - Paraschiv, Marius A1 - Gamba, Julien A1 - Burke, Tim A1 - Hohlfeld, Oliver A1 - Tapiador, Juan A1 - Vallina-Rodriguez, Narseo T1 - Mis-shapes, Mistakes, Misfits: An Analysis of Domain Classification Services T2 - ACM Internet Measurement Conference 2020, IMC ’20, October 27–29, 2020, Virtual Event, USA N2 - Domain classification services have applications in multiple areas,including cybersecurity, content blocking, and targeted advertising.Yet, these services are often a black box in terms of their method-ology to classifying domains, which makes it difficult to assesstheir strengths, aptness for specific applications, and limitations. Inthis work, we perform a large-scale analysis of 13 popular domainclassification services on more than 4.4M hostnames. Our studyempirically explores their methodologies, scalability limitations,label constellations, and their suitability to academic research aswell as other practical applications such as content filtering. Wefind that the coverage varies enormously across providers, rangingfrom over 90% to below 1%. All services deviate from their docu-mented taxonomy, hampering sound usage for research. Further,labels are highly inconsistent across providers, who show littleagreement over domains, making it difficult to compare or combinethese services. We also show how the dynamics of crowd-sourcedefforts may be obstructed by scalability and coverage aspects aswell as subjective disagreements among human labelers. Finally,through case studies, we showcase that most services are not fitfor detecting specialized content for research or content-blockingpurposes. We conclude with actionable recommendations on theirusage based on our empirical insights and experience. Particularly,we focus on how users should handle the significant disparitiesobserved across services both in technical solutions and in research. KW - Network KW - Network measurement KW - Information systems KW - Clustering and classification KW - Web applications KW - Web searching and information discovery Y1 - 2020 UR - https://eprints.networks.imdea.org/2183/1/paper.pdf SN - 978-1-4503-8138-3 U6 - https://doi.org/10.1145/3419394.3423660 SP - 598 EP - 618 ER -