How unique and traceable are usernames?

Daniele Perito*, Claude Castelluccia, Mohamed Ali Kaafar, Pere Manils

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference proceeding contributionpeer-review

124 Citations (Scopus)


Usernames are ubiquitously used for identification and authentication purposes on web services and the Internet at large, ranging from the local-part of email addresses to identifiers in social networks. Usernames are generally alphanumerical strings chosen by the users and, by design, are unique within the scope of a single organization or web service. In this paper we investigate the feasibility of using usernames to trace or link multiple profiles across services that belong to the same individual. The intuition is that the probability that two usernames refer to the same physical person strongly depends on the "entropy" of the username string itself. Our experiments, based on usernames gathered from real web services, show that a significant portion of the users' profiles can be linked using their usernames. In collecting the data needed for our study, we also show that users tend to choose a small number of related usernames and use them across many services. To the best of our knowledge, this is the first time that usernames are considered as a source of information when profiling users on the Internet.

Original languageEnglish
Title of host publicationPrivacy Enhancing Technologies
Subtitle of host publication11th International Symposium, PETS 2011 : proceedings
EditorsSimone Fischer-Hubner, Nicholas Hopper
Place of PublicationLondon ; New York
PublisherSpringer, Springer Nature
Number of pages17
ISBN (Electronic)9783642222634
ISBN (Print)9783642222627
Publication statusPublished - 2011
Externally publishedYes
Event11th International Symposium on Privacy Enhancing Technologies, PETS 2011 - Waterloo, ON, Canada
Duration: 27 Jul 201129 Jul 2011

Publication series

NameLecture Notes in Computer Science
ISSN (Print)0302-9743
ISSN (Electronic)1611-3349


Conference11th International Symposium on Privacy Enhancing Technologies, PETS 2011
CityWaterloo, ON


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