Title: On the Internet Someone Knows You Are a Dog Balachander Krishnamurthy, AT&T Labs - Research We have been examining the leakage of privacy on the Internet: how information related to individual users is aggregated as they browse seemingly unrelated Web sites. Thousands of Web sites across numerous categories, countries, and languages are studied to generate a "privacy footprint". I report on a longitudal study consisting of multiple snapshots of examination of such diffusion over five years. I'll talk about the technical ways by which third-party aggregators acquire data, the depth of user-related information acquired, the techniques for protecting privacy diffusion and limitations of such techniques. Such increasing aggregation of user-related data is carried out by a steadily decreasing number of entities: a handful are able to track users' movement across almost all of the popular web sites. Virtually all the protection techniques have significant limitations highlighting the seriousness of the problem and the need for alternate solutions. I will also talk about a recent discovery of large-scale leakage of personally identifiable information (PII) via Online Social Networks (OSN). Third-parties can link PII with user actions both within OSN sites and elsewhere on non-OSN sites. 4:30 PM Computer Science Small Auditorium (Room 105) Host: Jennifer Rexford