UK police hack encrypted phone chat network to arrest 'untouchable' criminals

British police say they have carried out their biggest operation ever, arresting "iconic" crime figures and smashing thousands of conspiracies including murder plots after infiltrating an encrypted communications service used by criminals.

The National Crime Agency (NCA) said the cracking of the encryption used by EncroChat, which offered a secure mobile phone instant messaging service and was used by criminals to coordinate their activities, had allowed detectives across the country to make almost 750 arrests.

The agency said it also meant a specialist team had been able to stop rival gangs carrying out kidnappings and executions, "successfully mitigating over 200 threats to life".

"Together we’ve protected the public by arresting middle-tier criminals and the kingpins, the so-called iconic untouchables who have evaded law enforcement for years, and now we have the evidence to prosecute them," NCA Director of Investigations Nikki Holland said in a statement.

The NCA said it had been working with international partners since 2016 to crack EncroChat which it described as a bespoke encrypted global communications service used exclusively by criminals.

Two months ago, French and Dutch investigators infiltrated the platform — which had 60,000 users worldwide and around 10,000 in the United Kingdom — and shared the data via Europol, allowing the authorities to monitor criminals' messages and movements.

EncroChat, which has now been shut down, had advised its users to throw away their handsets on June 13 after realising it had been compromised.

However, British police have made 746 arrests, claimed 54 million pounds (A$97.4 million) in criminal cash, seized 77 firearms, including an assault rifle and sub-machine guns, and more than two tonnes of drugs, the NCA said.

It added that entire networks had been dismantled in the most significant operation of its kind.

Other European law enforcement agencies have also used the information to target crime groups.

London's Metropolitan Police said it had charged 99 people as part of its investigations and made its largest ever single cash seizure of 5 million pounds (A$9m) in one operation.

Met Police Commissioner Cressida Dick said it was the most significant activity in her career and a huge blow to organised crime in London, but also "just the beginning" of the investigation.

"Through this work with our international partners, we have significantly developed our understanding of organised criminality in London and the ways in which some of our most prolific and dangerous offenders operate," she said.

"We know who they are and we have seen what they are doing and who they are doing it with.

"We will not rest until they have seen justice."

ABC/wires