Australia’s intelligence chief said that a “hive” of spies had been operating in the country for years.
Mike Burgess did not name any country behind the network, but said the undercover agents appeared to be “highly trained”.
The group will study and “potentially seduce” targets, including judges, journalists and veterans, he said.
He added that it shows the threat posed by foreign spies is at an all-time high.
Speaking at his annual threat assessment in Canberra, the head of the Australian Security and Intelligence Organization (Asio) outlined a “concerted campaign” to infiltrate Australian media to shape reporting and obtain information on sources.
According to him, the “hive” planned to offer journalists paid study trips to another country where spies with a “home country advantage” would try to get information to use.
And Mr Burgess also detailed the end of plots by two different countries to physically harm Australians – a week after the government revealed an Iranian plot to target a dissident in Australia had been foiled.
He again did not name the countries, but said critics of foreign regimes were targeted.
“In one case, the special service began monitoring a human rights defender and planned to lure the target offshore, where this person could be, quote, ‘disposed of,'” he said.
“In another case, a lackey was sent to find specific dissidents and, quote, ‘deal with them.’
Mr Burgess said Asio had weeded out the spies after an “intense and sustained” campaign.
“They were good but Asio was better… working with our partners we removed them. The hive remained in history,” he said.
But the threat posed by foreign intelligence is increasing, Mr Burgess said, particularly after Australia signed the Aukus security agreement with the US and UK.
“Asio is… busier than ever in our 74-year history. Busier than the Cold War, busier than 9/11, busier than the rise of the caliphate.”
“From where I’m sitting, it looks like hand-to-hand combat.”
Mr Burgess also used his speech to criticize the thousands of “reckless” Australians who advertise their security clearances on social media, as well as ex-Australian military personnel participating in foreign military training programs.
“It’s very important that our allies know that we can keep our secrets and keep their secrets,” Mr Burgess said.
