The Biden administration sanctioned two Chinese nationals and a Wuhan-based company Monday that allegedly targeted critical infrastructure sectors in the U.S. as part of an expansive hacking effort.

The Treasury Department levied sanctions against Zhao Guangzong and Ni Gaobin, as well as the Wuhan Xiaoruizhi Science and Technology Company, which the agency accused of acting as a front for China’s top spy agency.

“The United States is focused on both disrupting the dangerous and irresponsible actions of malicious cyber actors, as well as protecting our citizens and our critical infrastructure,” Brian Nelson, under secretary of the Treasury for terrorism and financial intelligence, said in a statement.

An arm of China’s Ministry of State Security allegedly operated in part through the Wuhan Xiaoruizhi Science and Technology Company, conducting “a wide variety of computer network exploitation and computer intrusion activities,” according to the Justice Department.

The hackers, part of the group known as APT31, targeted “some of America’s most vital critical infrastructure sectors,” as well as staff at the White House; the departments of Justice, Commerce, the Treasury and State; and members of Congress, according to the Treasury.

The Justice Department unsealed indictments against Guangzong, Gaobin and five other Chinese nationals on Monday, charging them with conspiracy to commit computer intrusions and conspiracy to commit wire fraud for their role in the hacking group.

“The Justice Department will not tolerate efforts by the Chinese government to intimidate Americans who serve the public, silence the dissidents who are protected by American laws, or steal from American businesses,” Attorney General Merrick Garland said in a statement.

“This case serves as a reminder of the ends to which the Chinese government is willing to go to target and intimidate its critics, including launching malicious cyber operations aimed at threatening the national security of the United States and our allies,” he added.