Were it not for a digital black box that recorded everything on IDT’s network, along with Mr. Ben-Oni’s tenacity, the attack might have gone unnoticed.

Scans for the two hacking tools used against IDT indicate that the company is not alone. In fact, tens of thousands of computer systems all over the world have been “backdoored” by the same N.S.A. weapons. Mr. Ben-Oni and other security researchers worry that many of those other infected computers are connected to transportation networks, hospitals, water treatment plants and other utilities.

An attack on those systems, they warn, could put lives at risk. And Mr. Ben-Oni, fortified with adrenaline, Red Bull and the house beats of Deadmau5, the Canadian record producer, said he would not stop until the attacks had been shut down and those responsible were behind bars.

“The world is burning about WannaCry, but this is a nuclear bomb compared to WannaCry,” Mr. Ben-Oni said. “This is different. It’s a lot worse. It steals credentials. You can’t catch it, and it’s happening right under our noses.”

And, he added, “The world isn’t ready for this.”

Targeting the Nerve Center

Mr. Ben-Oni, 43, a Hasidic Jew, is a slight man with smiling eyes, a thick beard and a hacker’s penchant for mischief. He grew up in the hills of Berkeley, Calif., the son of Israeli immigrants.

Even as a toddler, Mr. Ben-Oni’s mother said, he was not interested in toys. She had to take him to the local junkyard to scour for typewriters that he would eventually dismantle on the living room floor. As a teenager, he aspired to become a rabbi but spent most of his free time hacking computers at the University of California, Berkeley, where his exploits once accidentally took down Belgium’s entire phone system for 15 minutes.

To his parents’ horror, he dropped out of college to pursue his love of hacking full time, starting a security company to help the city of Berkeley and two nearby communities, Alameda and Novato, set up secure computer networks.