Everyone has an information footprint—a trail of information you leave behind as you use technology. For example, your information footprint may include search terms you've used, your location, your demographic information, and even your interests. Because online records are usually backed up and duplicated, much of your information footprint is permanent.
Abstaining from online activities does not necessarily mean you won't have an information footprint. Many companies and service providers record and store your information online, even if your interactions with them are strictly offline. Many of the devices and technologies we use communicate with each other electronically; this is often called the Internet of Things. Credit cards, electronic toll passes, RFID tags, DVR players, and remote home-climate-control systems all share information. For example, RFID-based devices (keycards, passports, microchip implants for pets) contain radio transmitters that broadcast each tag’s unique ID. In addition to letting you enter a building (or a country), this information can also be used to track your movements.
Even if devices aren’t directly connected to the Internet, their readings may end up stored in an online database. Water, electricity, and telephone companies all keep records of how much you use their services. Before you use a device or service, it’s good to think about what information it might be tracking, who might use that information in the future, and for what purposes.
What’s in a Footprint?
There are several related parts to your information footprint. The most obvious is data that you intentionally share, such as emails, social media posts, and filled-out forms. Information can also be shared about you. Friends may post about you on social media, and companies can sell data about your shopping records. Governments are digitizing many public records and making them widely available online (e.g., property records, birth and death records, and in some states, court records). Finally, most Internet activities are logged—or tracked—automatically, and your phone or computer shares its IP address (its unique numerical identifier) every time you visit a website.
All of your digital activities generate metadata. Metadata is loosely defined as "data about data," and it’s often used to find and organize information. For example, digital photos often include the time the photo was taken. This allows you to easily find your most recent photos. Wireless service providers collect information about what numbers you call, how long the calls are, and what cellphone towers pick them up. This metadata is used for billing and for determining where new towers may be needed. However, it may also leak information about your phone calls, even though the providers cannot listen to the calls themselves.
Data collection varies depending on your activities. When you use a shopping website, it might track the time you visited, how long you stayed on the website, and what products you viewed. Some websites even track how long you pause your mouse pointer over an image or link (because it indicates interest). Because your computer shares its IP address with the website, and because IP addresses are connected with geographic location, the website will also know approximately where you logged in from. These are only a few examples of data and metadata that is tracked and recorded. There are many more.
Individual Data Points Add Up
Putting together data (and metadata), often from different sources, to discover new information is called inference. For example, some Stanford researchers wanted to find out how much they could learn from analyzing cell phone metadata. In one case, they were able to use a long phone call with a family member, and subsequent calls to her local Planned Parenthood, with one final call a month later, to infer that a participant had an abortion. In that study, the inferences were drawn by humans. Computers don't necessarily (yet) have all of the background information to make such an inference, but on the other hand, they can compare much more data much more quickly using sophisticated search techniques.
Limiting Who Sees Your Footprint
You can limit who sees your information footprint by talking to your service providers, being selective when you share information online, and adjusting your device and app settings to optimize privacy. Your footprint may still be large, but it will be significantly more private.