There are two main classifications for digital footprints: passive and active. A passive digital footprint is created when data is collected without the owner knowing, whereas active digital footprints are created when personal data is released deliberately by a user for the purpose of sharing information about oneself by means of websites or social media.
Passive digital footprints can be stored in many ways depending on the situation. In an online environment a footprint may be stored in an online data base as a "hit". This footprint may track the user IP address, when it was created, and where they came from; with the footprint later being analyzed. In an offline environment, a footprint may be stored in files, which can be accessed by administrators to view the actions performed on the machine, without being able to see who performed them.
Active digital footprints can also be stored in many ways depending on the situation. In an online environment, a footprint can be stored by a user being logged into a site when making a post or change, with the registered name being connected to the edit. In an off line environment a footprint may be stored in files, when the owner of the computer uses a keylogger, so logs can show the actions performed on the machine, and who performed them. One of the features of keylogger is to monitor the clipboard for any changes as the user will sometimes have a very good habit of copying and pasting passwords and taking screenshots.
Tony Fish expounded upon the possible dangers of digital footprints in a 2007 self-published book. The closed loop takes data from the open loop and provides this as a new data input. This new data determines what the user has reacted to, or how they have been influenced. The feedback then builds a digital footprint based on social data, and the controller of the social digital footprint data can determine how and why people purchase and behave.
On the World Wide Web, the internet footprint; also known as cyber shadow, electronic footprint, or digital shadow, is the information left behind as a result of a user's web-browsing and stored as cookies. The term usually applies to an individual person, but can also refer to a business, organization and corporation.
Information may be intentionally or unintentionally left behind by the user; with it being either passively or actively collected by other interested parties. Depending on the amount of information left behind, it may be simple for other parties to gather large amounts of information on that individual using simple search engines. Internet footprints are used by interested parties for several reasons; including cyber-vetting, where interviewers could research applicants based on their online activities. Internet footprints are also used by law enforcement agencies, to provide information that would be unavailable otherwise due to a lack of probable cause.
Social networking systems may record activities of individuals, with data becoming a life stream. Such usage of social media and roaming services allow digital tracing data to include individual interests, social groups, behaviours, and location. Such data can be gathered from sensors within devices, and collected and analyzed without user awareness.
Digital footprints are not a digital identity or passport, but the content and meta data collected impacts upon internet privacy, trust, security, digital reputation, and recommendation. As the digital world expands and integrates with more aspects of life, ownership and rights of data becomes important. Digital footprints are controversial in that privacy and openness are in competition. Scott McNealy, CEO of Sun Microsystems, said in 1999 Get Over It when referring to privacy on the Internet. This later became a commonly used quote in relationship to private data and what companies do with it.
While digital footprint can be used to infer personal information, such as demographic traits, sexual orientation, race, religious and political views personality, or intelligence without individuals' knowledge, it also exposes individuals private psychological sphere into the social sphere. Lifelogging is an example of indiscriminate collection of information concerning an individuals life and behaviour. There are ways to make your digital footprint difficult to track. Illustrating examples of the usage or interpretation of data trails can be found at the example of Facebook-influenced creditworthiness ratings, the judicial investigations around German social scientist Andrej Holm, advertisement-junk mails by the American company OfficeMax  or the border incident of Canadian citizen Ellen Richardson.
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Kieron O’Hara- Lifelogging: Privacy and empowerment with memories for life (Tuffield, Mischa M. and Shadbolt, Nigel (2009))