A federal judge in the capital of Brasilia ordered the arrests of Gustavo Henrique Elias Santos, Suelen Priscila de Oliveira, Danilo Cristiano Marques and Walter Delgatti Neto. They live in three different cities in São Paulo state, but allegedly met in the countryside town of Araraquara.
The judge said the group invaded messaging app accounts of Moro, two federal judges and two federal police investigators. Later a federal forensics analyst said the group might have hacked into more than 1,000 phones, including the one of Economy Minister Paulo Guedes.
The ruling was issued Friday by judge Vallisney de Souza Oliveira but not made public until Wednesday.
Moro, who also heads Brazil's federal police, said on June 5 that his phone had been hacked.
Four days later, the website The Intercept Brasil and other associated media outlets started publishing reports based on leaked messaging app exchanges between Moro and prosecutors dating back to the minister's time as a judge in a corruption investigation known as "Operation Car Wash," which led to the arrests of many of Brazil's business and political elite, including former President Luiz Inácio Lula da Silva.
Oliveira's ruling does not establish a direct link between the arrests and the reported exchanges, which have caused a major stir in Brazilian politics and led Moro to testify in Congress in a turbulent environment.
The judge said in his decision that "there are strong indications the suspects formed a criminal organization to commit crimes, and joined together to violate the phone secrecy of several Brazilian authorities through the invasion of the Telegram app."
Oliveira also said two members of the group made suspicious transactions estimated at $167,000 between April 18 and June 29.
Ariovaldo Moreira, an attorney for suspects Gustavo and Suelen Priscila, said much of those funds came from bitcoin negotiations. The two deny any wrongdoing the lawyer said.
The Associated Press could not find lawyers for suspects Danilo Cristiano Marques and Walter Delgatti Neto.
Federal police investigator João Vianey Xavier Filho said the four suspects have a history in financial crimes.
Moro said on Twitter the suspects were "the source of trust to those who published the alleged messages obtained through crime."
The Brazilian justice minister does not acknowledge the veracity of the exchanges reported and insists even if they were true there would be no wrongdoing in the statements made to Car Wash prosecutors.
Most of the reported exchanges focus on conversations of federal prosecutor Deltan Dallagnol, the spearhead of the Car Wash task force. A separate investigation is being conducted in the state of Paraná to determine whether Dallagnol's phone was hacked.
The Intercept Brasil and its partners never revealed the source of the messages they published, which suggested illegal interference of Moro in Dallagnol's prosecution job in the da Silva case, among other exchanges.
Editor Glenn Greenwald said the website had already been handed the reported messages when Moro claimed he had been hacked.
"Sergio Moro is cynically trying to explore these arrests to cast doubt on the authenticity of the journalistic material," Greenwald said. "But the evidence that he rejects is too big for that to work on anyone."
The newspapers Folha de S.Paulo and El Pais, magazine Veja and radio BandNews say they have verfied the authenticity of the messages, and associated with The Intercept Brasil to report on the case.
A Brazilian Supreme Court justice and a prominent federal prosecutor, among others, have also confirmed the content of the published messages.
Moro is hailed by many Brazilians as an anti-corruption hero, but is criticized by others that see him as an anti-leftist zealot.
His credibility as an unbiased and tough judge in the sprawling Car Wash probe was put in doubt after the reports based on leaked messages.
Da Silva, who was president in 2003-2010, was convicted of corruption and money laundering over a beachfront apartment that prosecutors say he received from a construction company in exchange for lucrative government contracts. He denies he is guilty.