By Emilee Rader
If you use a mobile phone with location services turned on, it is likely that data about where you live and work, where you shop for groceries, where you go to church and see your doctor, and where you traveled to over the holidays is up for sale. And U.S. Immigration and Customs Enforcement is one of the customers.
The U.S. government doesn’t need to collect data about people’s locations itself, because your mobile phone is already doing it. While location data is sometimes collected as part of a mobile phone app’s intended use, like for navigation or to get a weather forecast, more often locations are collected invisibly in the background.
I am a privacy researcher who studies how people understand and make decisions about data that is collected about them, and I research new ways to help consumers get back some control over their privacy. Unfortunately, once you give an app or webpage permission to collect location data, you no longer have control over how the data is used and shared, including who the data is shared with or sold to.
Why mobile phones collect location data
Mobile phones collect location data for two reasons: as a by-product of their normal operation, and because they are required to by law.
Mobile phones are constantly scanning for nearby cell towers so that when someone wants to place a call or send a text, their phone is already connected to the closest tower. This makes it faster to place a call or send a text.
To maintain quality of service, mobile phones often connect with multiple cell towers at the same time. The range of the radio signal from a cell tower can be thought of as a big bubble with the cell tower in the center. The location of a mobile phone can be calculated via triangulation based on the intersection of the bubbles surrounding each of the cell towers the phone is connected to.
In addition to cell tower triangulation, since 2001 mobile phone carriers have been required by law to provide latitude and longitude information for phones that have been used to call 911. This supports faster response times from emergency responders.
How location data ends up being shared
When people allow webpages and apps to access location data generated by their mobile phones, the software maker can share that data widely without asking for further permission. Sometimes the apps themselves do this directly through partnerships between the maker and data brokers.
More often, apps and webpages that contain advertisements share location data via a process called “real-time bidding,” which determines which ads are shown. This process involves third parties hired by advertisers, which place automated bids on the ad space to ensure that ads are shown to people who match the profile of interests the advertisers are looking for.
To identify the target audience for the ads, software embedded in the app or webpage shares information collected about the user, including their location, with the third parties placing the bids. These third parties are middlemen that can keep the data and do whatever they want with it, including selling the data to location data brokers, whether or not their bid wins the auction for the ad space.
What happens to the data once it is shared
The data acquired by location data brokers is sold widely, including to companies called location-based service providers that repackage it and sell access to tools that monitor people’s locations. Some of these tools do things like provide roadside assistance. Others are used by police, government agencies and others to track down individuals.
In October 2025, news outlets reported that U.S. Immigration and Customs Enforcement had purchased a location surveillance tool from a company called Penlink that can track movements of specific mobile devices over time in a given location. Tools like this allow users to access location data from “hundreds of millions of mobile phones” without a warrant.
Why it matters
The invisible collection, sale and repackaging of location data is a problem because location data is extremely sensitive and cannot be made anonymous. The two most common locations a person visits are their home and where they work. From this information alone, it is trivially easy to determine a person’s identity and match it with the other location data about them that these companies have acquired.
Also, most people don’t realize that the location data they allowed apps and services to collect for one purpose, like navigation or weather, can reveal sensitive personal information about them that they may not want to be sold to a location data broker. For example, a research study I published about fitness tracker data found that even though people use location data to track their route while exercising, they didn’t think about how that data could be used to infer their home address.
This lack of awareness means that people can’t be expected to anticipate that data collected through the normal use of their mobile phones might be available to, for example, U.S. Immigration and Customs Enforcement.
More restrictions on how mobile phone carriers and apps are allowed to collect and share location data – and on how the government is allowed to obtain and use location information about people – could help protect your privacy. To date, Federal Trade Commission efforts to curb carriers’ data sales have had mixed results in federal court, and only a few states are attempting to pass legislation to tackle the problem.
Emilee Rader is Professor of Information at the University of Wisconsin-Madison.
Atwp says
Big brother watching where we go.
Laurel says
This is so sad.
It should be illegal to sell personal information.
Thomas Oelsner says
I have a real issue with this type of fear mongering. So let’s parse this out. First, what is done with the collected data is a subject on its own, which is for another discussion.
So why are you concerned why the entity is tracking you. Are you doing something illegal? By the very nature of you being in public your location is not private. Your conversations are private unless on a speaker phone. Next, if you are in a car accident or are lost this gives people an idea of where you are.
If there is a serial killer out there these are invaluable tools to finding the killer. This is exactly what happened with the Gilgo Beach murders. Cracking his cell phone and other digital fingerprints was a critical part to solving these murders.
So try a little nuance in your thanking.
Laurel says
Thomas Oelsner: Here’s a little “nuance” for you. If you read George Orwell’s novel “1984” you would see your own words. It was Big Brother, who is “watching you” who said “If you have nothing to hide, you have nothing to fear.” That’s one hell of a disclaimer, wouldn’t you say? Yet, you use it. Big Brother would watch people through their own TV’s inside their homes, not so different from today’s “smart” TVs.” People had no privacy and they were fiercely regulated by the government. The novel “1984” was published in 1949. It is a cautionary tale.
As for serial killers, “The odds of being murdered by a serial killer in the United States are approximately 1 in 645,000. This is based on the fact that around 2% of all murders are committed by serial killers, with a very small number of active serial killers at any given time.”
– AI Assist, Casino.org, Wikipedia
So, to me, it doesn’t seem logical that each and everyone of us should be monitored to the enth, just in case of a serial killer, so it appears that you are the fear mongering person here.
Sherry says
Right On Laurel!
Allyn Susan Feinsetin says
Am I mistaken, or have Democratic forces also designed websites to track the movements and operations of ICE–and encouraged protesters to use it and illegals to pay heed? And have some of these forces also publicly doxxed family members of ICE agents, resulting in their harrassment?
feddy says
You are not mistaken.
Sherry says
This is NOT about Republicans vs Democrats! You think you are not doing “anything wrong”, therefore no one will arrest you, really? Do you have the $$$$ to go to court to protect your privacy and rights?
If you are not driving, turn off the location tracker on your phone. Do not install “listening devices like Alexa in your home! Pay Attention. . . We are being warned:
https://www.youtube.com/watch?v=mSFUg8bGCXc
Robert Reich’s Views on the Problem
Surveillance Pricing: Reich highlights a practice where retailers use third-party data brokers to build comprehensive profiles (including location, income, and browsing history) to determine the maximum amount a person is willing to pay—a “pain point”—and charge them individualized prices, often without the consumer’s knowledge.
Infrastructure for Authoritarianism: He warns that the consolidation of data by private surveillance companies, such as Palantir, creates “digital dossiers” on every American, which could be leveraged by an authoritarian government to monitor, track, and silence dissent, bypassing traditional legal protections and oversight.
Erosion of Rights: Reich emphasizes that privacy is a fundamental right and its erosion is a threat to democracy itself, making individuals vulnerable to exploitation and control.
Recommended Actions for Protecting Privacy
Reich generally advocates for collective action and systemic change rather than solely individual fixes. His proposed actions center on political and regulatory measures:
Push for Legislation: He urges citizens to pressure elected representatives to enact strong data privacy laws and regulations that limit how corporations can collect and use personal data.
Support Regulatory Bodies: He points to the importance of strong regulatory action, such as that advocated by former FTC Chair Lina Khan, to rein in corporate data exploitation.
Public Awareness and Activism: Reich encourages widespread awareness of these issues, participation in demonstrations, and engaging with local and national media to highlight the dangers of merging surveillance capitalism with state power.
Boycotts and Corporate Pressure: He suggests boycotting companies that engage in harmful data practices or support what he views as authoritarian movements.
Sherry says
“Big Brother” is being rolled out TODAY! Please get “educated” on this “VITAL” subject. . . This from Robert Reich:
Friends,
The most dangerous corporation in America is one you may not have heard of.
It’s called Palantir Technologies, a Silicon Valley tech company that may put your most basic freedoms at risk.
Palantir gets its name from a device used in Tolkien’s The Lord of the Rings, in which a “palantir” is a seeing stone — something like a crystal ball — that can be used to spy on people and distort the truth. During the War of the Ring, a palantir falls under the control of the evil Sauron, who uses it to manipulate and deceive.
Palantir — co-founded by far-right billionaire Peter Thiel and its current CEO Alex Karp — bears a striking similarity.
It sells AI-based data platforms that let their clients, including governments, militaries, and law enforcement agencies, quickly process and analyze massive amounts of your personal data.
Whether it’s social media profiles, bank account records, tax history, medical history, or driving records, the tools that Palantir sells are used to help clients identify and monitor individuals — like you.
Why should this matter to you? Billions of your tax dollars are going to Palantir, and what Palantir is working on could be used against you.
As Palantir’s Karp says: “Palantir is here to disrupt and make the institutions we partner with the very best in the world and, when it’s necessary, to scare enemies and on occasion kill them.”
Early in his current term, Trump signed an executive order requiring government agencies to consolidate all of their information about you into one giant database — something that has never been done before. To help process this massive amount of information, Trump chose Palantir.
Trump claims this is about “efficiency.” But as one Silicon Valley investor described it, Palantir is “building the infrastructure of the police state.”
Data privacy experts warn that when government data is pooled together, it can be used by a tyrant to intimidate or silence opposition. The possibilities for abuse are huge. One of Palantir’s major projects is a new immigrant surveillance system for ICE’s deportations.
We’ve already seen Trump target people or organizations he considers enemies. Imagine if he could punish or deny services to individual Americans based on their political affiliation, whether they’ve attended a protest, or even posted an unflattering picture of him online.
Palantir could be giving Trump the power to do just this.
Palantir co-founder and Trump ally Peter Thiel has made no secret of his disdain for democracy, writing “I no longer believe that freedom and democracy are compatible.”
But when he speaks of “freedom,” he isn’t thinking about you. To Thiel, “freedom” means that he and his fellow tech oligarchs get to do what they want, without consequences, while the rest of us live in an authoritarian police state.
It’s a match made in Mordor — Trump gets the infrastructure to go after his enemies. Thiel gets to end American democracy.
The danger of Palantir’s AI-powered super database on all Americans is amplified by the vast wealth and power of those associated with it, and their apparent disdain for democratic institutions.
To protect democracy and our individual freedoms, we need to elect leaders who will defend the public from corporations like Palantir — not partner with them.
Tolkien’s palantir fell under the control of Sauron. Thiel’s Palantir is falling under the control of Trump.