Australian Federal Police said the Ghost app was marketed to underworld figures as "unhackable" and was used by hundreds of suspected criminals from Europe, the Middle East and Asia.

But, unbeknownst to users, global policing authorities hacked the network and were watching as the criminals discussed illicit drug trafficking, money laundering, homicides and serious violence.

Authorities made their move on Tuesday and Wednesday, arresting criminals from Italy, Ireland, Sweden, Canada and Australia -- including Jay Je Yoon Jung, the alleged "mastermind" of the app.

Europol executive director Catherine De Bolle said law enforcement from nine countries had been involved in the international sting.

"Today we have made it clear that no matter how hidden criminal networks think they are, they can't evade our collective effort," she said.

"This was a truly global game of cat and mouse, and today the game is up", Jean-Philippe Lecouffe, Europol's deputy executive director, told reporters in agency's headquarters in The Hague.

Authorities dismantled an Australian drug lab while weapons, drugs and more than one million euros ($1.1 million) in cash have been seized globally, the EU policing agency added.

Ghost, a kind of WhatsApp for criminals, was created nine years ago and could only be accessed via modified smartphones that sold for about Aus$2,350 (US$1,590).

The hefty price tag included a six-month subscription to the Ghost app and tech support, Australian police said Wednesday, and users were required to purchase an ongoing subscription.

French police traced the creator's location to Australia and joined forces with local police to target the platform.

The app's creator regularly pushed out software updates but in 2022, Australian police were able to hijack those updates to access encrypted content.

For two years, authorities watched as Ghost became more popular and criminals exchanged messages -- including 50 death threats that Australian police said they were able to thwart.

Several thousand people worldwide use Ghost and around 1,000 messages are exchanged on it every day, according to Europol.

There were 376 phones with the Ghost app installed in Australia alone.

In one case, police intercepted an image of a gun to someone's head and were able to save that person within the hour, Australian Federal Police assistant commissioner Kirsty Schofield said.

Ireland, which was second in terms of Ghost users, was able to dismantle "a primary drugs trafficking route into our country and in doing so have seized drugs with an approximate street value of 16 million euros", Justin Kelly, assistant police commissioner, was quoted as telling The Irish Times.

- Breaking the unbreakable -

Hacking into encrypted apps on phones has become increasingly challenging for authorities, but not impossible.

Three years ago, a similar network -- called ANOM -- led to 800 arrests worldwide.

Little did they know, ANOM was produced and distributed by the FBI, allowing US and other nations' law enforcement to decrypt 27 million messages, many of which related to criminal activity.

Australian Federal Police deputy commissioner Ian McCartney said after the ANOM network unravelled, Ghost started to "fill that space".

He added that law enforcement was aware of other similar encrypted apps and that he hoped some of these would be shut down within 12 months.

Europol said encrypted communications had become "increasingly fragmented" after other services were disrupted or shut down, leading criminals to diversify their methods.

- Element of 'surprise'-

McCartney said the Ghost app creator from New South Wales lived at home with his parents and did not have a criminal history.

The "computer geek" was driven by profit and was "slightly surprised" when police arrested him Tuesday, McCartney said.

Schofield added that police had to act quickly given the man had the ability to "wipe the communications on the system".

"Our tactical teams were able to secure him and the devices within 30 seconds of entry," she said.

The 32-year-old was charged with five offences, including supporting a criminal organisation, which carries a sentence of up to three years' imprisonment.

He appeared in a Sydney court on Wednesday and was denied bail, with no future court date set.

Another 38 people have been arrested across Australia.

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