Media outlets claim they have confirmed reports that Australian law-enforcement agencies are stripping metadata from mobile phone companies, gaining huge amounts of information on the general public and non-suspicious people.

Fairfax Media says it has confirmed that state and federal police departments are actively using a technique known as a “tower dump”.

The dumps give police data about the identity, activity and location of any phone that is connected to a targeted cell towers, and reports say a typical sweep will cover multiple towers and mobile providers at once.

In the same week as new legislation around metadata is being considered, reports say agencies already take more than they need.

Police officials are refusing to comment on the practice, but some defenders say ‘tower dumps’ are one of the most powerful tools for tracking down criminals, and are only used when police have few leads.

Privacy advocates say it would clearly be useful for police, but because it is done in secret it has no judicial oversight, and breaches personal privacy by targeting thousands of innocent people. They also question what happens to the data collected once an investigation is complete.

Fairfax reporters say no warrant is required to request a tower dump, and while police departments all declined to comment it has “confirmed” that the investigational tool was often used by NSW Police at least.

Mobile phone companies say the tower dumps occur “on occasion”.

“Mobile network operators receive requests from Australian law-enforcement agencies to provide communications information from a specific tower,” a Vodafone spokesperson told Fairfax.

“These requests usually cover short periods and the information provided is only metadata.”

‘Only metadata’ is a phrase that has evoked different levels of concern among authorities, as discussed in this video. 

Metadata includes information on the time, duration and destination of a phone call, as well as the location of a mobile phone when it periodically “checks in” with nearby towers.

The content of calls, voice and text messages cannot be uncovered through this technique.

Telstra has neither confirmed nor denied being asked for customers’ data, but has indicated it belies tower dumps to be unlawful.

“A request for non-content information on the use of a particular tower during a specified period of time may be lawful under certain circumstances,” a Telstra spokesperson told reporters.

Similarly, Optus would only say that it assisted “law-enforcement and national security agencies as required in the legislation...”

Greens Party spokesperson for communications Scott Ludlam said it is another iteration of the global digital surveillance approach of “take everything” and ask questions later.

“It’s another example where [agencies] are collecting the entire haystack in order to find the needle,” Senator Ludlam said in an interview with Fairfax.

“What we've seen with other techniques like this is there is no requirement to destroy the material that is collected incidentally after an investigation is complete,” he said.

“What we need is transparency as to what's being done and who is doing it... ultimately I think we need a lawful warranting process to start to apply to [requests for data] like this.”

The Attorney-General’s Department’s most recent annual report showed that round 330,000 requests for metadata were made by law-enforcement agencies in 2012-13, but it does not indicate whether tower dumps are included in this count.