A Closer Look at Location Data: Privacy and Pandemics

In this series, Privacy and Pandemics, the Future of Privacy Forum explores the challenges posed by the COVID-19 crisis to existing ethical, privacy, and data protection frameworks, and will seek to provide information and guidance to companies and researchers interested in responsible data sharing to support public health response. Future posts will examine pandemic-tracking mobile apps, regulatory guidance across the world, and more.

Part 1: A Closer Look at Location Data

• Contributors: Chelsey Colbert (Policy Counsel, Mobility and Location); Polly Sanderson (Policy Counsel, Legislative Analysis); Katelyn Ringrose (Policy Fellow); Dr. Sara Jordan (Policy Counsel, Artificial Intelligence and Ethics).
• Governments around the world are considering whether and how to use mobile location data to help contain the virus: Israels government passed emergency regulations to address the crisis using cell phone location data; the European Commission requested that mobile carriers provide anonymized and aggregate mobile location data; and South Korea has created a publicly available map of location data from individuals who have tested positive.
• Public health agencies and epidemiologists have long been interested in analyzing device location data to track diseases.
• Finally we discuss some preliminary ethical and privacy considerations for processing location data.
• Researchers and agencies should consider: how and in what context location data was collected; the fact and reasoning behind location data being classified as legally sensitive in most jurisdictions; challenges to effective anonymization; representativeness of the location dataset (taking into account potential bias and lack of inclusion of low-income and elderly subpopulations who do not own phones); and the unique importance of purpose limitation, or not re-using location data for other civil or law enforcement purposes after the pandemic is over.

What is precise location data? 

• Precise location data, or mobility data, involves information about how devices and people move through spaces over time.
• Even the most basic connectivity, or the ability to send and receive wireless content on devices, has to involve information about where those devices are located.
• For example, providers of wireless services must know where devices are located because they provide the service through local cell towers and networks.
• However, most researchers analyzing COVID-19 are interested in highly precise information about where devices (and therefore people) are located over time.
• The fact that an individual is located in Washington, DC is not sufficient for tracking an infectious disease, but information such as works in the same building or attended the same restaurant at the same time as a diagnosed person (precise location) can be very useful.

Who has access to location data? 

• Location data is held by a variety of commercial entities that provide different services, including as part of the core functionality of a device (mobile phone carriers and operating systems), as part of a consumer-facing feature (mobile apps), or as part of tracking in physical spaces that relies on device connectivity (Internet of Things):
  • Mobile phone carriers. Cell phone carriers know where phones are located because they provide the service through local cell towers. This is also how 911 calls are increasingly traced.
  • Operating Systems. Providers of mobile operating systems — Android (Google) and iOS (Apple) — also know where devices are located and use the data to provide functionality. In addition, some users may have opted in to that data being used to improve location services.

  
   

How is location data collected?

• When most people think of location data, they think of GPS (Global Positioning System). In fact, there are many other ways to infer where devices are located, most used in some combination by carriers, OS’s, apps, and others. Commonly used methods include: GPS; Cell Towers; Wi-Fi Networks; and Beacons (among others). Each provides a different level of precision and can be used for different purposes:
  • GPS. Smartphones and other devices can detect location via satellite GPS (Global Positioning System) independently of any telephone or internet reception. The accuracy of GPS signals varies widely, and can be affected by weather, or physical interference — for example, it is much less accurate in urban areas or inside of large buildings. As a result, modern cell phones combine GPS with other forms of location signal (Wi-Fi, Bluetooth) to gain a more accurate location determination.
  • Cell Towers. Cell towers have a main function, which is to be used by carriers to provide cell service. As a result, mobile carriers (such as AT&T, Sprint, Verizon, T-Mobile, and others in the United States) know where devices are located because they know which cell towers the devices connect with. In addition to this core function, cell towers also emit unique “Cell Tower IDs,” which can be freely detected. There are many private and public databases of the Cell Tower IDs associated with mapped locations of known cell towers. As a result, the proximity of nearby cell towers (and the signal strength of their IDs) can be used to infer where a device is located. Find your local cell towers here (OpenCellID). 
  • Wi-Fi Networks. Mobile devices can infer their location by scanning for nearby Wi-Fi networks. Nearby networks or “access points” might include, for example, neighbors’ Wi-Fi, or the Wi-Fi available in cafes and shops. Large databases exist of the unique identifiers (MAC addresses and SSID) of wireless routers and their known locations, with companies such as Mozilla and Combain reporting databases of up to 3 billion unique Wi-Fi networks. Despite the relatively public nature of these identifiers, most (but not all) commercial databases offer an Opt Out mechanism for users who prefer that their own network not be included. In 2011, Google created an approach for opting-out a particular access point from being included in its database, which involves appending the phrase “_nomap” to the end of the wireless router’s SSID. Mozilla similarly honors the _nomap method, but other databases do not, or offer their own opt-outs.

Ethical and Privacy Considerations for Location Data

• Lawmakers are beginning to navigate whether and how to make use of the many sources of commercial location data. As they do so, we recommend that they consider: how and in what context location data was collected (described above), as well as: the fact and reasoning behind location data being classified as legally “sensitive” in most jurisdictions; challenges to effective “anonymization”; representativeness of the location dataset (taking into account potential bias and lack of inclusion of low-income and elderly subpopulations who do not own phones); and the unique importance of purpose limitation, or not re-using location data for other civil or law enforcement purposes after the pandemic is over.
  • Location data is legally sensitive. In most jurisdictions, location data is treated as a special category of data subject to greater protections, such as heightened security standards, and the requirement of affirmative express consent. For example, the longstanding approach of the US Federal Trade Commission (FTC) has been to require affirmative consent for location data. In 2016 the FTC settled with ad platform InMobi for failing to respect users’ choice not to agree to share location data with apps. Affirmative express consent is also a feature of most US legislative proposals from 2018-2020, such as the proposed California Privacy Rights Actof 2020; and U.S. Senator Cantwell’s proposed Consumer Online Privacy Rights Act. The U.S. Supreme Court has also held that location data carries unique sensitivities because of its ability to reveal highly sensitive data about people’s behaviors, patterns, and personal life, most recently in Carpenter v. United States (requiring law enforcement to obtain a warrant for cell site location data). In the EU, access to location data is normally regulated as a matter of confidentiality of telecommunications, by the strict provisions of the ePrivacy Directive which require individual consent (with very narrow exceptions).
  • Location data is very challenging to fully “anonymize.” Many government entities are interested in gaining access to “anonymous” or “anonymous and aggregated” location data, to observe population-level trends and movements. While in some cases this is possible, it is very challenging to make any dataset of individual precise location data truly “anonymous.” Even if unique identifiers are used instead of names, most people’s behavior can be easily traced back to them— for example, from the location of their home (where the device “dwells” at night). These challenges are not insurmountable, but policymakers should be very careful not to overpromise, and should treat location datasets as private, sensitive information. This means it should be subject to administrative, technical, and legal controls to ensure it remains protected and limited in who can access it and for what purposes. 
  • Even fully “aggregate” location data can sometimes be revealing. At times, even highly aggregated data about patterns of large groups of people (such as high-level heat maps) can inadvertently reveal information. In 2017, an interactive “Global Heat Map” of movements of users of the Strava fitness app inadvertently revealed the locations of deployed military personnel at classified locations. This incident highlights some of the wider ethical issues associated with open data and default public data sharing. In FPF’s privacy assessmentof the City of Seattle, we recommended that companies thoroughly analyze all risks, not only risks to privacy and re-identification, but also to “group privacy,” and impact on other values such as data quality, fairness, equity, and public trust.
  • Representativeness and bias are uniquely important for location datasets. Unfair data processing practices involving geolocation fall disproportionately on marginalized and vulnerable communities. As such, heightened privacy protections are especially critical for these groups. Voluntary apps, for example, are more likely to capture affluent communities. For example, a mobile app ‘Street Bump’ was released by a municipal authority in an attempt to crowdsource data to work out which roads it needed to repair. However, affluent citizens downloaded the app more than people in poorer neighborhoods. As such, the system reported a disproportionate number of potholes in wealthier neighborhoods, and could have led the city to distribute or prioritize its repair services inequitably. In contrast, mobile phone carrier data may be more representative, but may miss more of the elderly, very young, or lowest income people who may not own cellphones.
  • Purpose limitation is uniquely important in a crisis. Purpose limitation is a core guiding light of the US-based Fair Information Practice Principles (FIPPs) and the EU’s General Data Protection Regulation (GDPR). Because location data is sensitive and challenging to truly “de-identify” (i.e. to significantly reduce or eliminate all privacy risks), there is a serious concern that once collected by a public health agency for pandemic tracking, it could be retained or used for other purposes. Governments should consider how the location data was collected in the first instance (with users’ knowledge or consent?), and if the decision is made to repurpose it for pandemic tracking, it should be clearly siloed for that purpose and not re-used or retained for other civil or law enforcement uses. Researchers or agencies should have clear policies and procedures in place that describe the operational and technical aspects of data management.

Conclusion

• As COVID-19 continues to spread, we are facing global challenges to existing norms and best practices for data collection and use.
• In some cases, location and mobility data might provide one path to better understanding and combatting the pandemic.
• Governments and researchers seeking to address concerns and risks should ask: how and in what context the location data was collected; whether it is necessary and appropriate to achieving their goals (including whether the data is truly representative of the overall population and takes into account vulnerable populations such as the elderly); whether those goals can be achieved through less invasive means; and how that data will be used, safely stored, retained, or re-purposed following the conclusion of the pandemic.

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