How Cops Can Block Remote Wiping of Seized Cellphones with Aluminum Foil

Cops seizing and searching cellphones without a warrant is an issue contentious enough that it’s heading to the Supreme Court. A law professor is arguing warrantless searches should not be allowed, but gives police an easy idea to protect phones from remote data wiping while they wait for the legal go-ahead to search.

One of his techniques, wrap the phone in aluminum foil.

Aluminum foil can help block a signal from getting to a phone. A law professor suggests instead of allowing warrantless searches of phones, police take measures to protect the phone’s content while they wait for a warrant. (Photo:

Yes, a sheet of aluminum foil can cloak a phone, protecting it from being wiped of information potentially valuable to a case before a warrant is received.

Adam Gershowitz at William and Mary Law School believes the Supreme Court should “allow law enforcement to seize cell phones without a warrant and immobilize the devices until a magistrate determines whether to issue a warrant.”

Advocating for warrantless seizure only in situations of arrest, Gershowitz’s paper published on the Social Science Research Network last week suggests some data protection solutions that “fight fire with fire or, more aptly, to fight technology with technology.”

While still requiring a warrant to search the phone but protecting its contents, Gershowitz said “strikes a balance between the competing concerns of cellphone privacy and the need for police to preserve evidence.”

Wrapping the device in several sheets of foil is the cheapest and simplest of the data protection techniques law enforcement could take while waiting for a warrant.

“Anyone – including the police – can watch an instructional YouTube video about building a Faraday device,” Gershowitz wrote. “Or if the police do not want to build a structure, they can simply buy a roll of aluminum foil for $2 in a grocery store and leave it in their vehicle. When the police seize a phone, they simply have to wrap the phone in a few layers of aluminum foil and the chance of remote wiping of the phone will be almost completely eliminated.”

Watch the video Gershowitz references about building the signal-blocking device:

The next step up would be putting the phone in a microwave (keeping the microwave off) or a Faraday cage or bag:

Companies already manufacture Faraday bags designed specifically for law enforcement to hold cell phones and prevent remote wiping. Once placed into a Faraday bag, the phone can no longer communicate with the outside world and thus cannot be remotely wiped by a conspirator. The Department of Justice has recommended that agents place any seized cell phone in a Faraday bag as soon as possible to avoid remote wiping

faraday bag
A commercially made Faraday bag. (Photo: Disklabs)

The problem with a Faraday bag or cage is that the phone would still be able to clear data if the action was pre-programmed. Some messages and apps last anywhere from just a few second or minutes while others can disappear after a few days.

An option to solve this problem though is a Universal Forensic Extraction Device, which downloads a phone’s contents within minutes. These devices though can be expensive and come with other legal issues of law enforcement maintaining the information or reviewing it without a warrant.

Gershowitz pointed out the ACLU’s criticism of the Michigan State Police, which the advocacy group accused of downloading information from motorists cellphones, and said “there has been relatively little publicity about the UFED devices.” He noted the devices already being used by federal agencies and local police forces in New York, Los Angeles, Sacramento and elsewhere.

Gershowitz said although police departments “might prefer to have unrestricted authority to conduct warrantless cellphone searches,” the Fourth Amendment doesn’t guarantee law enforcement be ensured the “most convenient searching method.”

Given the amount of private data now stored on these devices, Gershowitz said the Supreme Court should “simply prohibit warrantless searches, allow police to seize the phones, and let evolving technology handle the rest.”

(H/T: Gizmodo)