Federal investigators have dismantled a massive telecom network hidden throughout the New York area that they said could have caused havoc in communications systems throughout New York City just as the annual United Nations General Assembly is getting underway in Manhattan.

The network included more than 100,000 SIM cards and 300 servers that could have interfered with emergency response services, shut down cellular service in the city, and sent and received encrypted messages, all as more than 150 leaders from around the world descended on New York City for the week, according to the Secret Service.

It’s unclear what the telecom network was to be used for and who was putting it in place, though the scale of the operation – the equipment was spread within a 35-mile radius of the UN headquarters in New York – and the equipment used could suggest a surveillance operation by a nation-state organization. Secret Service agents told journalists that by analyzing data on some of the SIM cards, they were able to identify links to at least one foreign nation as well as cartel members, according to The New York Times.

It’s also unknown right now if the UN General Assembly was the target of the operation.

In speaking with journalists, Matt McCool, special agent in charge of the Secret Service’s New York field office, suggested that nation-state actors used the system to send encrypted messages to organized crime groups, cartels, and terrorist organizations, according to CNBC.

Larger Investigation Leads to Discovery

The sprawling network was uncovered in August as part of a larger investigation by the Secret Service into what the agency called “telephonic threats’  – telephone threats –  made to three federal officials in the spring. The threats were made to a Secret Service official and two others who work in the White House, according to the agency.

Going through all the phone calls, text messages and any other communications that ran through the network will take time, McCool said.

“It can’t be understated what this system is capable of doing,” McCool said. “It can take down cell towers, so then no longer can people communicate. …. You can’t text message, you can’t use your cell phone. And if you coupled that with some sort of other event associated with UNGA … it could be catastrophic to the city.”

The organization that put together the hidden network was well-funded, given that the equipment involved as worth millions of dollars.

Targeting Critical Infrastructure

Foreign adversaries like China and Iran have, for several years, targeted critical infrastructure for espionage and disruption purposes. A Chinese nation-state threat group called Volt Typhoon was found hiding in the systems and networks of critical infrastructure networks in the United States, essentially lying in wait until a time came when they were told to disrupt services.

Another such group, Salt Typhoon, compromised the broadband networks of U.S. telecom giants to steal data and attain persistence, and also has targeted other organizations around the globe. In a report in August, United States intelligence agencies and counterparts from other countries outline how Chinese companies are supporting such nation-states in their activities.

Iranian-linked threat actors, such as Cyber Av3ngers, had attacked water systems in the United States and other countries, and, according to researchers with Check Point, the group has a history of targeting other critical infrastructure sectors, including electrical and transportation systems.

According to CNBC, the Secret Service’s McCool said there could be similar networks such as the one found in New York elsewhere in the country, adding that “it’d be unwise to think that there aren’t other networks out there being made in other cities in the United States.”