  We survey the literature on the privacy of trajectory micro-data, i.e.,
spatiotemporal information about the mobility of individuals, whose collection
is becoming increasingly simple and frequent thanks to emerging information and
communication technologies. The focus of our review is on privacy-preserving
data publishing (PPDP), i.e., the publication of databases of trajectory
micro-data that preserve the privacy of the monitored individuals. We classify
and present the literature of attacks against trajectory micro-data, as well as
solutions proposed to date for protecting databases from such attacks. This
paper serves as an introductory reading on a critical subject in an era of
growing awareness about privacy risks connected to digital services, and
provides insights into open problems and future directions for research.
