In 2020, a police department in Missouri paid a private company for access to a searchable database of phone location data. No warrant. No judge. A purchase order acquired it the way you buy printer toner.

The company was Fog Data Science, a Virginia firm founded in 2016 by two former Department of Homeland Security officials. Its product, Fog Reveal, let officers draw a polygon on a map, pick a date range, and see which devices had been inside it. The Electronic Frontier Foundation obtained contracts through public records requests showing subscriptions running between roughly $6,000 and $9,000 a year, with a base tier of 100 queries a month. Eighteen agency contracts were confirmed. Historical data reached back to at least June 2017.

Nine days before that purchase, the exact same data would have required a warrant if the department had asked Google for it.

The mechanism

The data doesn't come from the phone company. It comes from apps.

A weather app asks for your location to show you local conditions. A game asks for it to serve regional ads. You tap Allow because the request makes sense in the moment. What happens next is invisible: the app's advertising software transmits your coordinates along with a device advertising identifier to a network of companies that buy and resell that stream.

The advertising identifier is the part that matters. It is a string of characters your phone hands to advertisers so they can recognize you across different apps. It isn't your name, and it doesn't need to be. A device that sits at one address every night and a second address every weekday has told you both where someone lives and where they work. The identifier stitches every subsequent sighting to the same person.

Fog's upstream source appears to have been a company called Venntel. The evidence is unusually direct. Fog Reveal's own code submits queries to a web address containing the path /Venntel/GetLocationData. When the Missouri State Highway Patrol produced its copy of Fog's service agreement, the document still carried undeleted header text reading "Venntel Analytics, Inc. Event Data Licensing Agreement". A company changed the name on a contract and missed a line.

Fog's marketing material claimed access to 250 million devices and hundreds of billions of records. Those figures came from the company's own sales pitch and were repeated in press coverage. EFF was explicitly unable to verify them and gave reasons for doubting them. Treat them as a vendor's claim about its own product, which is what they are.

The historical parallel

In the Second World War, Allied intelligence spent enormous effort breaking the German naval Enigma. The four-rotor M4 machine entered service on 1 February 1942 and shut the codebreakers out for most of that year.

The fleet kept transmitting, and the transmissions themselves could be measured. Shore stations and shipborne direction-finding equipment took bearings on U-boat radio signals. Cross the bearings from several stations and you have a position, without reading a single decrypted word. Volume, timing, and origin of traffic revealed patrol patterns and concentrations. The protected channel stays locked. The unprotected exhaust around it surrenders the position anyway.

The human mechanic

The purchase is easy in a way the warrant is not, and that asymmetry is the entire story.

A warrant means an affidavit, a supervisor, a prosecutor, a judge, and a written record that a defense attorney will eventually read. A subscription means a purchase order and a login. It is the same data with radically different friction.

There is a second effect that is subtler and more corrosive. A warrant is scoped to a person, a place, and a window of time. A subscription is a standing capability. Once the login exists, the marginal cost of one more query is zero. The thing an officer does with a zero-cost capability at eleven at night on a hunch is not the thing they would write into an affidavit at nine in the morning.

Records obtained by EFF did not show routine oversight of how these queries were used. That is an absence of documentation, not proof of misuse. It is worth stating precisely that nobody has demonstrated systematic abuse. What is demonstrated is that the paperwork which would let anyone check does not appear to exist.

What the Court did, and what it didn't

In July 2024, the Fourth Circuit Court of Appeals decided United States v. Chatrie. The court ruled that police conducted a Fourth Amendment search when they used a geofence warrant to access Google Location History because the warrant lacked particularity and swept up the location data of innocent bystanders. It was a significant ruling establishing that broad digital dragnets violate constitutional privacy protections.

That is a genuine win.

Now the gap.

Every stage of Chatrie concerned a warrant compelling Google to produce data. The question of whether police may buy functionally identical data on the open market was never before the court. The opinion does not resolve it.

The front door now has a lock on it. The side door is a purchase order.

Whether that door stays open is unsettled. The argument that buying this data is constitutionally different from compelling it will be fought in lower courts. Today it has not been decided.

The countermeasure, honestly priced

Turn off the advertising identifier. On iPhone: Settings, Privacy & Security, Tracking, and switch off Allow Apps to Request to Track. On Android: Settings, Privacy, Ads, and delete the advertising ID. It takes under a minute and costs nothing.

This is not cosmetic. Records indicate Apple's App Tracking Transparency measurably reduced Fog Reveal's usefulness to police. A former analyst for a police department said the company deliberately stayed quiet about it so that people would not realize the setting mattered and would leave it on.

What it does not do: it removes the identifier that stitches sightings together, but it does not stop apps you have granted location permission from knowing where you are.

Audit the permissions. Open the same settings menus under Location. Set everything to While Using or Never. Anything set to Always is reporting your position while it sits closed in your pocket. It takes fifteen minutes for a phone with a lot of apps on it. You will want to repeat it after major OS updates, which sometimes reset these.

What none of this reaches: your carrier still knows where your phone is because that is how cell service works. Apps you actively use while location is on still see you. Data already sold is already sold. There is no delete button for a record that changed hands in 2019.

The realistic outcome is that you stop generating new material for this market. That is meaningful. It isn't erasure, and anyone selling you erasure is selling you something.

The Missouri purchase order is not a scandal. Nothing about it was hidden, illegal, or unusual. A department bought a commercial product from a company that was entitled to sell it, using data that people had technically agreed to share.

That is the part to sit with. Appellate courts are beginning to rule that this data is constitutionally protected when police compel it. The exact same data remains available for purchase. The thing that determines which rule applies is not the sensitivity of the information but the paperwork used to obtain it. Constitutional protections attach to procedures. Markets route around procedures. Until someone closes it, the gap is where you live.

Stay paranoid.

Sources

[DOCUMENTED] United States v. Chatrie, 107 F.4th 319 (4th Cir. 2024)

[DOCUMENTED] Carpenter v. United States, 585 U.S. 296 (2018)

[DOCUMENTED] Electronic Frontier Foundation, Fog Data Science investigation (public records obtained by request, including contracts, pricing, and the Missouri State Highway Patrol service agreement)

[REPORTED] Associated Press coverage of Fog Reveal, including the company's own claims about scale, which EFF was unable to verify

[REPORTED] Former police analyst's account of App Tracking Transparency's effect on Fog Reveal's utility

[INFERRED] The conclusion that recent geofence warrant rulings create difficulty for the compel/purchase distinction is analysis, not holding. The courts did not address commercial purchase.