Where have you been? A Study of Privacy Risk for Point-of-Interest
  Recommendation
Kunlin Cai Jinghuai Zhang Will Shand Zhiqing Hong Guang Wang Desheng Zhang Jianfeng Chi Yuan Tian
As location-based services (LBS) have grown in popularity, the collection of
human mobility data has become increasingly extensive to build machine learning
(ML) models offering enhanced convenience to LBS users. However, the
convenience comes with the risk of privacy leakage since this type of data
might contain sensitive information related to user identities, such as
home/work locations. Prior work focuses on protecting mobility data privacy
during transmission or prior to release, lacking the privacy risk evaluation of
mobility data-based ML models. To better understand and quantify the privacy
leakage in mobility data-based ML models, we design a privacy attack suite
containing data extraction and membership inference attacks tailored for
point-of-interest (POI) recommendation models, one of the most widely used
mobility data-based ML models. These attacks in our attack suite assume
different adversary knowledge and aim to extract different types of sensitive
information from mobility data, providing a holistic privacy risk assessment
for POI recommendation models. Our experimental evaluation using two real-world
mobility datasets demonstrates that current POI recommendation models are
vulnerable to our attacks. We also present unique findings to understand what
types of mobility data are more susceptible to privacy attacks. Finally, we
evaluate defenses against these attacks and highlight future directions and
challenges.