Facebook has restricted public access to a feature that has been used to pursue war criminals, expose human rights abuses and identify corrupt officials.

Key points: Graph Search was an invaluable tool for law enforcement, investigative journalists and human rights defenders

Graph Search was an invaluable tool for law enforcement, investigative journalists and human rights defenders Facebook's move may be connected with a shift towards a privacy-focussed business model

Facebook's move may be connected with a shift towards a privacy-focussed business model Researchers have used Graph Search to uncover war crimes and save lives

The social media giant — which had vowed to become more transparent about its operations — last week quietly "paused" public access to a feature called Graph Search without giving any indication when or if open access might be restored.

The throttling of access represents one of the most visible and significant changes to its network in the wake of the Cambridge Analytica scandal last year.

Graph Search was a feature which allowed users to extract specific public data from Facebook's vast trove of stored information, above and beyond what simple keyword searches could achieve.

"Facebook's actions are a direct attack on human rights and [a] clear message that they stand alongside violent regimes," said Gregory Waters, a Middle East researcher at the University of California, Berkeley.

"This isn't just about enabling investigators to find information, it's also about being able to fact-check governments."

'A very powerful tool'

Launched in 2013, the feature allowed users to search for social connections, at a time when Facebook was promoting itself as being on a mission to make the world more open and connected.

At a basic level, Graph Search enabled someone to search for, say, every male nurse who "liked" both Scott Morrison and Coldplay, or find specific words posted by users on specific days.

But it also allowed people to unearth publicly available personal information about other users, including every public comment, like or share — making it difficult for someone to hide their past.

That made Graph Search invaluable for law enforcement, intelligence agencies, human rights groups and investigative journalists.

"This [decision to shut Graph Search] has taken a very powerful tool from the hands of civil society," said Nick Waters, a senior investigator with open source intelligence pioneer Bellingcat.

Mr Waters had been mapping airstrikes against civilians in Yemen when access to the feature was throttled, and he feared the governments launching those attacks would remain unaccountable if Facebook did not restore it.

Graph Search played a part in exposing the Russian connections to the downing of MH17 — which killed 38 Australians — after Ukrainian and Dutch researchers used it to identify Russian-backed rebels operating near the crash site.

It has also helped prosecute war criminals, was used by organisations trying to help abused women in Bangladesh, and was utilised by ABC News to establish a connection between the Christchurch gunman and white nationalists.

"Time and time again, our research integrates eyewitness interviews with corroborating social media content," said Amnesty International's Sam Dubberley.

"When the platforms make changes, especially without consultation, this makes our job of finding and verifying the content harder, and means that the human rights defenders taking the largest risk are not heard."

He said his organisation was in contact with Facebook but "not a lot seems to be happening".

Focus on privacy

While Facebook has not given a detailed explanation for the "pause", it is thought to be related to the company's recent announcements about a change of focus.

"The future is private," Facebook co-founder and CEO Mark Zuckerberg said in April, responding to a series of data privacy and security lapses which have left the company wounded and on the defensive.

Bellingcat's Henk Van Ess said the blocking of access to Graph Search jeopardised several ongoing investigations, including one monitoring human trafficking.

"This is impacting some of the most important institutions in society — it helped save lives," he said.

Mr Van Ess said despite Facebook's claims about protecting the privacy of its users, those who were paying to advertise on the platform still had access.

"Facebook now considers searching public data a privacy disaster, but they continue to allow advertisers to target the audience with ads with way more privacy-related options," he said.

In a statement to news website Vice, a Facebook spokesperson said: "The vast majority of people on Facebook search using keywords, a factor which led us to pause some aspects of Graph Search and focus more on improving keyword search.

"We are working closely with researchers to make sure they have the tools they need to use our platform."