New documents released on Wednesday by the American Civil Liberties Union of California show that for the last several years, police in the city of Anaheim, California—home of Disneyland—have been using an invasive cell phone surveillance device, known as a "dirtbox." The ACLU obtained the 464 pages of documents after it sued the Anaheim Police Department last year over the agency’s failure to respond to its public records request concerning such surveillance-related documents.

The DRTBox has been described by one Chicago privacy activist as a "stingray on steroids," referring to the controversial cell-site simulator that spoofs cell towers to locate phones and intercept calls and texts.

Last year, both the Department of Homeland Security and the Department of Justice (which oversees the FBI) said that they would require a warrant during stingray deployments. A new law that took effect in California on January 1, 2016 would also require use of a warrant for a cell-site simulator.

"If a city of a few hundred thousand can have this kind of arsenal, it raises questions as to what similar cities across America might have it as well," Matt Cagle, an ACLU lawyer, told Ars.

Anaheim is now the third city in the US, after Los Angeles and Chicago, known to deploy this particular surveillance technology. It has also been used by the National Security Agency in France and likely elsewhere. (The spy technology was also mentioned briefly in the first episode of the new X-Files miniseries.) A heavily-redacted letter shows that among other devices, the APD likely acquired the DRT1201B, the same one used by the Air Force years earlier.

The Chicago activist, Freddy Martinez, who is currently suing his city's police department over access to stingray-related records, told Ars that these new documents raise notable questions. He points out that a newer version, the DRT120C, is capable of full digital interception and recording.

"It's troubling that DRT is in The Intercept's catalog and that local police departments are buying similar models," he said. "It makes me wonder if this surveillance is doing full scale voice decryption on possibly hundreds of people."

In a blog post, Cagle wrote:

While the documents do not discuss Anaheim’s aerial use of the device, they include an email from Lt. Dave Vangsness, head of the Anaheim Police Department’s Air Support Bureau, discussing what appears to be a memorandum of understanding for the dirtbox. Vangsness has publicly boasted about an Anaheim-owned 10-seat Cessna that "can quietly conduct surveillance during narcotics investigations." It’s worth noting that Anaheim police purchased the same dirtbox model sought by the U.S. Air Force around 2012. All of this raises troubling questions about how exactly Anaheim used their device and just how many people have been affected.

The Wall Street Journal's 2014 revelation that the United States Marshals Service had been flying dirtboxes from five major airports across America raised concerns with privacy scholars. "Regarding using planes as cell towers, that is problematic in my opinion. It strikes me as analogous to the use of stingrays," Brian Owsley, a former federal magistrate judge and current law professor at the University of North Texas, told Ars . "Therefore, I think the government would need to obtain a search warrant based on probable cause consistent with the Fourth Amendment.

"I think the growth of the use of drones will further exacerbate this problem," he added.

Ganking your crypto keys

As Reveal reported in August 2015, a DRTBox can "simultaneously break the encryption of communications from hundreds of cellphones at once. A 2011 purchase order for this equipment by the Washington Headquarters Services, a branch of the Pentagon, states the devices can retrieve the encryption session keys for a cellphone ‘in less than a second with success rates of 50 to 75% (in real world conditions).’"

Various federal law enforcement agencies, including the United States Marshals Service, the US Special Operations Command, Drug Enforcement Administration, FBI, and US Customs and Border Protection are also known to use the snooping devices.

The dirtbox gets its name from the Boeing subsidiary that manufactures them—Digital Receiver Technology or DRT. On its website, Boeing used to tout that DRT creates "a miniature yet powerful receiver measurement capability to test and monitor wireless signals... While other products require multiple scanners linked together to perform similar system measurements, Boeing offers this capability within a single portable product."

It is not clear if the APD is still using the gear. One 2014 e-mail released by the ACLU from an APD police investigator to a colleague said that the "DRT gear is sitting on a shelf now because it’s become obsolete and is not [REDACTED]. DRT really fell behind the curve and has not come out with updates in about two years."

The APD refused to answer Ars’ questions as to how many DRTBoxes the agency has, under what circumstances they are deployed, and whether the agency has changed its policy to require a warrant for their use—as is required under a new 2015 state law.

"As you are aware, the Anaheim Police Department and the City of Anaheim are involved in civil litigation regarding this issue," Sgt. Daron L. Wyatt, an APD spokesman, told Ars by e-mail. "As such, the police department will not comment on anything that may be deemed related to the civil action and we are referring all inquiries to the Anaheim City Attorney's Office."

Neither the city attorney, nor the city manager, nor Mayor Tom Tait responded to Ars’ request for comment.

UPDATE 12:00pm ET: In an e-mail sent to Ars, FBI spokesman Christopher Allen said: "I cannot comment on investigative tools or techniques that may have been used in specific cases. But certainly anytime we use a cell site simulator we adhere to the policies in place at the time."