WARSAW, Poland -- A Polish Senate commission opened an investigation into the use of powerful spyware against government critics by hearing testimony Monday from cybersecurity experts, who compared targeting of opposition figures under the right-wing government to methods used by the Kremlin against critics in Russia.

       John Scott-Railton and Bill Marczak, senior researchers with the Citizen Lab, a research group based at the University of Toronto, told the seven-member committee they were able to confirm that data was stolen from the phone of a Polish senator, Krzysztof Brejza. That came on top of their reports in late December that Brejza and two others — a Polish lawyer and a prosecutor — were hacked aggressively with Pegasus, spyware produced by Israel's NSO Group.

       The revelations have shocked many Poles because Pegasus is a tool meant to be used by governments to fight terrorists and other dangerous criminals. Many view it as a human rights violation to use it against domestic opponents who criticize the government but pose no danger to society.

       In Brejza's case, his phone was hacked multiple times in 2019, mostly when he was running the opposition’s parliamentary election campaign. Messages from his phone were doctored and used in a smear campaign against him in the heat of the race, which the ruling right-wing Law and Justice party narrowly won.

       Speaking by video link, the two experts also confirmed to the committee that an operator first started registering the Pegasus infrastructure in November 2017, which was just a month or two after Polish media established that the contract with the Polish government was finalized.

       The Law and Justice party has rejected calls by the opposition for an investigation into the hacking in the lower house of parliament, or Sejm.

       In reaction, the Senate, where the opposition has a small majority, approved forming a committee to investigate evidence that the three government critics were hacked with the spyware. Sen. Marcin Bosacki, the committee's chairman, said the step was needed “due to the deepest concern for our democracy and the future of the Polish state.”

       Bosacki said one of the probe's aims will be to determine whether the hacking of Brejza’s phone altered the outcome of the 2019 election, arguing that a state in which secret services have an influence on the election process ceases to be a democracy.

       Still, only the Sejm, whose roles include supervising the government, can launch an inquiry with full investigative powers, including calling witnesses. The Senate can invite witnesses but not require them to appear. Law and Justice senators voted against establishing the committee and refused to accept seats they were offered on it.

       Bosacki concluded Monday's two-hour questioning of the two witnesses by saying it was a good start to clarifying the “aggressive” use of Pegasus technology against a senator and two others.