The Garda National Cyber Crime Bureau has been part of an internationally supported operation targeting the Hive Ransomware Group.
Operation Downbreaker has shut down the servers and technical infrastructure utilised by the group.
The FBI on Thursday revealed it had secretly hacked and disrupted the prolific ransomware gang, a manoeuvre that allowed the US bureau to thwart the group from collecting more than $130 million in ransomware demands from more than 300 victims.
At a news conference, US Attorney General Merrick Garland, FBI Director Christopher Wray, and Deputy US Attorney General Lisa Monaco said government hackers broke into Hive's network and put the gang under surveillance, surreptitiously stealing the digital keys the group used to unlock victim organisations' data.
They were then able to alert victims in advance so they could take steps to protect their systems before Hive demanded the payments.
"Using lawful means, we hacked the hackers," Monaco told reporters. "We turned the tables on Hive."
News of the takedown first leaked on Thursday morning when Hive's website was replaced with a flashing message that said: "The Federal Bureau of Investigation seized this site as part of coordinated law enforcement action taken against Hive Ransomware."
Detective Chief Superintendent at the Garda National Cyber Crime Bureau, Barry Walsh said: "This is an excellent result that has come from a lot of painstaking work carried out by gardaí in the Cyber Crime Bureau and together with our colleagues across the world.
"It underscores the immense value of co-ordinating a collective law enforcement response to emerging criminality.
"The Hive Ransomware Group has caused a great deal of distress to people in Ireland, and has upset their daily lives in more ways than one. This is not just about the monetary loss suffered by victims, but the significant disruption that a cyberattack causes.
"We will further maximise on this work and stay focused on targeting the tactics and methods of cybercriminals and which affect victims here in Ireland.”
Hive's servers were also seized by the German Federal Criminal Police and the Dutch National High Tech Crime Unit.
"Intensive cooperation across national borders and continents, characterised by mutual trust, is the key to fighting serious cybercrime effectively," said German police commissioner Udo Vogel in a statement from police and prosecutors in the state of Baden-Wuerttemberg, who assisted in the probe.
Hive ransomware has been identified as a major threat to international security, compromising the data of large multinationals in Europe.
Over 1,300 companies worldwide have fallen victim to the associates of the Hive Ransomware Group since November.
They have paid almost €100 million in ransom payments.
