Original URL: http://www.theregister.co.uk/2005/12/22/tracked_by_mobile_phone/

Tracked by cellphone

The astounding arguments of the US government

By Mark Rasch

Posted in Security, 22nd December 2005 23:54 GMT

Comment We know that technology can be used to track people's location via a cellphone, but how difficult is it for law enforcement to get a court order and do this legally?

An old physics joke recounts that Werner Heisenberg (of the uncertainty principle) is pulled over by the police for speeding one night. The police officer asks the professor, "Do you have any idea how fast you were going?" Heisenberg replies, "No, but I know exactly where I am."

Being tracked via your phone

Recent court cases in the United States raise the question of the standard required when the police want to know exactly where you are, using your cell phone to track you down. The issue again raises the question of how new technologies can invade privacy rights, and how quantitative changes in the type and amounts of data collected and stored result in qualitative changes in privacy rights. These require a reexamination of even established laws of privacy and of probable cause. These precedents also apply to entities like ISPs and telephone companies that routinely collect massive amounts of data about individuals which may be subject to eventual discovery or disclosure. It is important that we establish and apply the correct legal standard for obtaining this information now.

Whenever you carry (much less use) a cell phone that is turned on, the cellular network is constantly "scanning" to determine where you are so that it can route telephone calls to the appropriate cell location. By examining the relative signal strength of three of these cells, through a process called "triangulation" the cell provider can determine - with relatively low level of precision, where you are at any point in time. Other technologies employed by cell providers, such as those employed with E-911 services, can determine your location with greater precision. Finally, some cell phones are also equipped with GPS capabilities, which passively receive certain data from geosynchronous satellites to enable the phone (but not the provider) to determine its precise locations - often within a matter of feet.

This digital location information, coupled with high-speed internet access in some cell phones, can be a great boon to users. They can use cell phones to locate restaurants, theaters, or other entertainment in their area, make reservations or arrange for carry out as they travel. They might use such technology to locate family members, including children. In a disaster situation (assuming the cell towers continue to work), the technology might be useful in locating survivors - well, at least locating the survivor's cell phones. One can imagine their use by law enforcement agencies in kidnapping cases.

Such data is already being used by cellular providers to determine demand for and therefore location of new cell towers. It is not difficult to imagine the economic usefulness of this data as well. Cell providers can collect this information, link it to specific users as well as the demographic information provided when the subscriber initiated the cellular contract. They can then sell, lease or otherwise provide this information to third parties. In addition, cell providers are increasingly becoming indistinguishable from internet service providers, as people use their handheld devices to access the internet from anywhere. Thus, cell providers will have the ability to collect records of every place you have been, who you have talked to, and collect location and content of text messages, e-mails, web traffic, IP video and downloaded or streaming audio. It is time to set some rules on what information can be collected, and what can be done with all of this information.

Location, Location, Location

In at least three separate cases, the US government has attempted unsuccessfully to obtain court order to require the cellular providers to provide them information about the location of a cellular customer gleaned from the triangulation of the signals they have received. This in and of itself is remarkable. When the government wants a court order to obtain a wiretap, a pen register, or to search for or seize documents or records, it files the paperwork ex parte and in camera. What this means is that only the government is represented. If the government believes that a certain law applies, it and only it presents the law to the magistrate judge. In fact, for virtually all such applications, the records relating to the application are sealed - either automatically by statute or as a matter of routine by application of the government. Thus, we have no idea how many times the federal government has gone to court to obtain cell phone location data and been granted the data, with no questions asked. The fact that three magistrates refused the government's request is itself amazing.

What the government was trying to do in these three cases, one in the Eastern District of New York (Long Island), one in Maryland, and one in Texas, was to obtain "prospective" cell location data. That is, they wanted the court to order the cell companies to tell them whenever a particular cell phone moved, where it went, and how long it was there.

It is important to note that all three of the courts recognized that the government could get this information if it needed it. All three courts also recognized that they had the authority to order such prospective cell location data. At issue was the legal standard the government had to meet to obtain the information.

Legal requirements for cellphone location information

Essentially, there are four legal standards for the government to obtain cellphone location information. First and lowest is a pen register or a trap and trace device. This is simply a record of the telephone calls made (from and to) and the time of each call. Because of an assumption that these are merely records of the telephone company, and therefore one can't possible have an expectation of privacy in such records, for a court to order the production of such records (even prospectively), all that needs to happen is for a prosecutor to certify that the records are relevant to some ongoing investigation. Indeed, with such a certification in hand, the court is not even permitted to question or challenge this - it MUST give the government the power to obtain the records from the provider.

Next on the list is stored communications and subscriber records. This would include things like stored SMS messages, stored emails, and the information provided to the telephone company when the customer created the account. To obtain these records, the government would need to meet a slightly - and only slightly - higher standard than the above. The government would have to demonstrate specific and articulable facts as to why such records are relevant to an ongoing investigation. Congress made a distinction between communications in transmission or in temporary storage versus those that are incident to transmission and are actually stored. In the former case, the "interception" of the electronic communication is similar to eavesdropping on a telephone call, and in Congress' opinion the same kind of warrant should be required. For stored communications however, since the records already exist and are stored somewhere, its more like seizing a printed document (a printed e-mail). Thus, Congress presumed that a lower standard should apply.

A third standard applies for the installation of "tracking devices" to monitor the location of people or things. To install or monitor such a device, the government would have to show (albeit in an affidavit that the target never gets to see or challenge in advance) that it was more likely than not that this would reveal evidence of some crime by somebody - and not necessarily that the person being tracked was committing a crime.

Finally, as noted above, the highest standard is for the interception of the contents of communications (voice or electronic) in transmission. These warrants can be issued either on a finding of probable cause by a regular court, or on certain finding by a special intelligence court, or as recently disclosed by the New York Times, by executive order and with no warrant (as was done with the National Security Agency).

Government argues "real time" electronic data doesn't exist

In the New York, Maryland and Texas cases, the government wanted to track the location of cell phone holders in advance under the lower standard of simply demonstrating some facts as to why they wanted it, rather than the slightly higher standard of providing probable cause. They argued that the records are merely stored records of "communications." The courts in these cases pointed out that the signal being measured (for signal strength to determine location) was not a "communication" under the statute. The government then argued that, despite language in the statute mandating that phone companies cooperate in pen registers or trap and trace installations (the infamous Communications Assistance to Law Enforcement Act, or CALEA), which stated that "the authority for pen registers and trap and trace devices cannot be used to obtain tracking or location information…" that they could get such information under a lower standard than probable cause.

The next government argument is somewhat astounding. The courts all agreed that the lower standard of "articulable facts" would apply to the disclosure by the cell phone company of "historical call site information". That is, if your phone company retained records of where you were, the government could get them with a subpoena, a search warrant, or even a warrant on a lower standard. Indeed, the court recognized that the government could demand that the phone company retain and not destroy such records in anticipation of a later court order. The higher "probable cause" standard applied only to the creation and dissemination to the cops of records that didn't yet exist. This is where the astounding argument comes in - the government claimed (with a straight face, no less) that as soon as the cell towers in question determined your location and recorded this fact, these were now "historical" records subject to the lower standard. Thus, according to the government, there is no such thing as "real time" data or even data "in transmission."

As a technical matter, this is likely true. Indeed, I have argued that there is no such thing as interception of packets "in transmission." The packets have to be stopped, copied, and reassembled to be read. Nevertheless, the law makes a distinction between historical data and real time data. That the government would seek to extinguish this distinction in this case does not bode well for the government's position in other cases. The government could then argue that it could listen in on your VOIP calls with nothing more than a subpoena (for which no probable cause is required) because all it is doing is looking at "historical" packets - albeit merely hundredths of a second in the past. This is clearly the opposite of the delicate balance Congress sought to strike. Thus, it appears that the government is seeking to convert all interceptions into seizures of "historical" data, and adopt the lower standards for such data.

What about your privacy?

All of this discussion is somewhat beside the point, however. The real issue is whether people have a reasonable expectation of privacy in the location data in the first place. As a general rule, the US Supreme Court has adopted what I call the "breeze rule". Effectively, if I am outside (and can feel a breeze), I probably don't have an expectation of privacy in what I am doing. Thus, if I am growing pot in my backyard with a 20 foot un-scalable fence, the cops with a helicopter and a telescope (or, presumably a geostationary satellite and a keyhole telescope) can monitor me without probable cause or a warrant. If I am walking or driving down the street, the cops can follow me without a warrant or even suspicion. The same goes for using technology to enhance the ability to search. Thus, drug, money or explosive sniffing dogs can sniff me, my briefcase, my car, and presumably my house (if there is no trespass to do so) without any legal restriction. If I walk into my house however, the Supreme Court has ruled, the cops can't for example use and infrared detector to monitor my activities in the house without some kind of warrant.

Thus, the cops can follow me around, either directly or using technology. If they use their eyes, binoculars, a telescope, a helicopter or other similar technologies, they don't need probable cause or a warrant. If they install a tracking device on me, however, they do need probable cause. But what do they need to simply obtain records from the phone company (whether in real time, slightly historical or historically) to accomplish the same thing?

The real problem here is that the cell phone providers have the ability to collect, store, collate and aggregate location data on hundreds of millions of people. These records then become a commodity: subject to use, sale, transfer, subpoena or other discovery. In past cases, the government (with a warrant) has turned on people's On*Star GPS tracking and telephones to track them and listen in on their conversations. Technically, the government isn't "installing" a tracking device on you - it is merely retrieving the records of a tracking device you didn't know you already had. What this means is that Congress needs to step in and establish guidelines for both private, public, law enforcement and intelligence acquisition and use of this passive tracking information. Will they do this? As Dr. Heisenberg might say, it's uncertain.

Mark D. Rasch, J.D., is a former head of the Justice Department's computer crime unit, and now serves as Senior Vice President and Chief Security Counsel at Solutionary Inc.

This article was first published at SecurityFocus

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