Three private Chinese firms have allegedly facilitated China in executing one of the most audacious hacking operations, which included spying on text messages from the Kamala Harris and Donald Trump campaigns in 2021. This assertion comes from a coalition of U.S. agencies and 12 allied international governments.

The endeavor, known as Salt Typhoon, infiltrated telecommunication giants globally, such as AT&T and Verizon last year. This breach allowed potential access to text and phone communications among millions, as well as the capability to track individuals’ locations.

A comprehensive 37-page technical report released on Wednesday by entities including the FBI, the National Security Agency, and the Cybersecurity and Infrastructure Security Agency—as well as intelligence and law enforcement agencies from nations like Australia, Canada, Germany, Japan, and the United Kingdom—indicates the campaign, active since 2021, also targeted global government, transportation, lodging, and military infrastructure networks.

An FBI spokesperson told NBC News in an emailed statement that Salt Typhoon has hacked more than 200 companies across 80 companies.

NBC News disclosed in July that the Department of Defense had determined earlier this year that Salt Typhoon had infiltrated at least one state’s National Guard network, remaining undetected for nearly a year.

The firms implicated in supporting China’s Ministry of State Security (MSS) during this operation include Beijing Huanyu Tianqiong Information Technology, Sichuan Zhixin Ruijie Network Technology, and Sichuan Juxinhe Network Technology.

The Treasury Department had already sanctioned Sichuan Juxinhe Network Technology for its involvement with Salt Typhoon activities in January, whereas the other two companies had not been previously accused by Western governments of engaging in international hacking endeavors.

Little information about the companies is available online, and they could not be reached for comment. A spokesperson for China’s embassy in Washington did not immediately respond to a request for comment.

It is remarkable that the three firms appeared to be actually functioning companies, not merely fronts for Chinese intelligence, according to Dakota Cary, a China analyst at the cybersecurity company SentinelOne.

“Which means the MSS (Ministry of State Security) effectively used three private companies working in collaboration to hit some of the most important collection targets on the planet,” Cary told NBC News.

“It is inconceivable the U.S. would ask a private company to hack Xi’s phone,” he added, referring to Chinese President Xi Jinping.

While Salt Typhoon does not exclusively hack telecommunications companies, it has proven remarkably adept at doing so. Its hack of AT&T and Verizon alone gave China access to phone data on more than a million people in the D.C. area.

That kind of access not only gives intelligence agencies the potential to spy on phone calls and text messages, but also to track people’s location, the report found.

“The data stolen through this activity against foreign telecommunications and Internet service providers (ISPs), as well as intrusions in the lodging and transportation sectors, ultimately can provide Chinese intelligence services with the capability to identify and track their targets’ communications and movements around the world,” it said.

AT&T and Verizon have both said that they have removed the hackers from their systems, although they remain vulnerable to being broken into again.