Data exhaust is the data generated as a byproduct of people’s online actions and choices.
Data exhaust consists of the various files generated by web browsers and their plug-ins such as cookies, log files, temporary internet files and and .sol files (flash cookies). In its less hidden and more legitimate aspect, such data is useful to improve tracking trends and help websites serve their user bases more effectively. Studying data exhaust can also help improve user interface and layout design. As these files reveal the specific choices an individual has made, they are very revealing and are a highly-sought source of information for marketing purposes. Websites store data about people’s actions to maintain user preferences, among other purposes. Data exhaust is also used for the lucrative but privacy-compromising purposes of user tracking for research and marketing.
Data exhaust is named for the way it streams out behind the web user similarly to the way car exhaust streams out behind the motorist. An individual’s digital footprint, sometimes known as a digital dossier, is the body of data that exists as a result of actions and communications online that can in some way be traced back to them. That footprint is broken down as active and passive data traces; digital exhaust consists of the latter. In contrast with the data that people consciously create, data exhaust is unintentionally generated and people are often unaware of it.
Security and privacy software makers struggle with the conflicting goals of marketing and privacy. User software designed to protect security and privacy often disrupts online marketing and research business models. While new methods of persistently storing tracking data are always in development, software vendors constantly design new methods to remove them.
See Michelle Clark's TEDx talk about digital footprints: