An industrial engineer from the University of Massachusetts has taken credit for breaking into the US Department of the Interior, Federal Reserve and the Bank of England.
The attack, which took place last week, is thought to be the largest in history.
The hackers used the name “NEO-T” to create a series of messages, including one that said “Northeast” and another that said: “We’re here to take you down”.
The hacker group called itself “NEXUS” and claimed responsibility for the attack.
Nexus claimed responsibility on Twitter, saying that it had “made the most powerful botnet malware ever seen”.
The FBI said it had been “aware of the malicious activity, but have not been able to identify the perpetrators”.”NEXus, with the help of other actors, compromised multiple systems within the federal government and was able to conduct significant financial and personal data compromise,” it said in a statement.
It added that “Nexuses’ activities and the malicious content they published, including malware, trojans, spyware, and other exploits, are designed to steal data, compromise systems, and wreak havoc on our nation’s financial systems and the cyber security of businesses across the country”.
The attack was first reported by news site Ars Technica.NEXS claimed responsibility in a tweet that read: “Nuclear reactor: This is the best place to test your new botnet!”
Nexas spokesperson Kristianne Gartland told ABC News that the hackers had taken credit.
“They’ve done what many companies have done and made the most effective botnet, malware, worm that we’ve ever seen,” she said.
The hackers used several different tools to create the malicious code.
“They are able to create very sophisticated and powerful malware and exploit that code in order to do things that are not easy for us to do,” Gartlands said.
Gartland said that the attacks “went down quite quickly” and that the FBI was investigating.
“We have not yet identified any specific victims and we’re not going to,” she added.
Nuclear reactors have been a focus of recent debate about the security of the technology, and the US has a long history of running them.
The Fukushima nuclear plant was the first to be decommissioned and the first reactors were decommissioning in the 1980s.
The Federal Emergency Management Agency has issued a warning about running nuclear reactors in the US, saying “any person, organization, or entity operating any reactor in the United States should be aware of the potential for attack”.
Nuclear power has been controversial for decades.
It is estimated that it accounts for one-third of the electricity generated in the country.
Nukes are also controversial, because they have been linked to climate change and nuclear waste.
The technology is considered highly polluting.
The US government has already banned nuclear reactors and plans to phase out their use by 2025.