The US is gathering data from thousands of mobile phones using fake communications towers on aeroplanes, according to the Wall Street Journal.
The programme run by the US Marshals Service, an agency of the US Justice Department, uses devices made by Boeing that mimic phone towers to trick mobiles into revealing their unique registration data, the report said, and has been in operation since 2007.
The devices, nicknamed ‘dirtboxes’, are flown on Cessna aircraft out of at least five major airports that are able to cover most of the US population and can collect information from tens of thousands of phones in a single flight.
The flights occur on a regular basis, the newspaper said, citing people familiar with the operations, who also said that the device used in the programme decides which phones belong to suspects and 'lets go' of non-suspect phones.
The device allows the authorities to bypass telephone companies, making it easier for them to locate suspects directly, the report said.
The Journal quoted Christopher Soghoian, chief technologist at the American Civil Liberties Union, as calling it "a dragnet surveillance programme. It's inexcusable and it's likely, to the extent judges are authorising it, they have no idea of the scale of it."
The newspaper said it was unknown what steps are being taken to ensure data collected on innocent people is not kept for future perusal by authorities.
A Justice Department official would not confirm or deny the existence of such a programme, the newspaper reports, saying such discussion would allow criminals and foreign powers to determine US surveillance abilities. The official added that department agencies comply with federal law, including by seeking court approval.
Although it can interrupt calls on some phones, authorities have made software changes to make sure it doesn't interrupt anyone calling the 911 emergency number for help, the Journal quoted one person familiar with the matter as saying.