The New York City Police Department has used covert cellphone spying devices known as Stingrays more than 1,000 times since 2008, indiscriminately sweeping up communications and tracking people's location, New York Civil Liberties Union said Thursday.

Stringrays are portable devices that simulate cellphone towers, forcing all nearby phones to connect to them and then secretly intercepting massive amounts of information, including location data and content of calls and text messages, according to data given to the New York Civil Liberties Union (NYCLU). NYPD records show that the devices have aided in solving a number of crimes including murders, rapes, kidnappings, shootings, bank robberies, identity theft and money laundering, reported The New York Times.

The NYPD disclosed that it has no written policy for using the devices and doesn't obtain a warrant before employing them. Rather, the department only needs to establish that the information is "relevant to an ongoing criminal investigation" and obtain a "pen register order" from a court, which is easier to get than a formal search warrant and does not require probable cause.

"If carrying a cellphone means being exposed to military grade surveillance equipment, then the privacy of nearly all New Yorkers is at risk," said Donna Lieberman, executive director of the NYCLU. "Considering the NYPD's troubling history of surveilling innocent people, it must at the very least establish strict privacy policies and obtain warrants prior to using intrusive equipment like Stingrays that can track people's cell phones."

The NYPD's deputy commissioner for legal affairs, Larry Byrne, insisted the department always establishes probable cause before asking a judge for a pen register order.

"As a matter of practice, we're doing more than what the state law requires us to do," he said during a press conference to defend the practice, according to The New York Post. "To dispel any misinformation about this, we will draft a policy internally to codify what has been our standard operating practice that we have not deviated from in any case."

The department's deputy chief for legal affairs, Kerry Sweet, said that the NYPD only collects information from the targeted phone number, not the content of calls and text messages of innocent people in the area.

"We do not pick up information from other people standing by, innocent bystanders, passersby. This does not lock on their phone numbers or pick up any information from their phones either," he said.

Stingrays were initially developed in 2003 and intended for military use, but over the past decade, the devices have been purchased by police departments across the country, with many pledging to the manufacturers that they would not disclose any details about how the devices function, according to the Times. The ACLU estimates that at least 59 police departments in 23 states use the devices, as well as at least 13 federal agencies, including the IRS, FBI and DEA.