SentinelOne listed on the New York Stock Exchange under a one-letter ticker, S, and raised $1.2 billion doing it. Its software sat on laptops, servers, and cloud machines, watching how programs behaved. When something acted like an attack, it could stop it and roll back the damage on its own. In June 2021, ransomware had just shut down a major American fuel pipeline, and companies were rushing to replace old antivirus tools.

Fight Machine With Machine

Tomer Weingarten, Almog Cohen, and Ehud Shamir founded the company in Israel in 2013 as Sentinel Labs, and later moved its headquarters to Mountain View, California. Older antivirus software looked for known bad files. SentinelOne bet that AI could judge behavior instead, and catch new attacks no one had seen before. It sold one platform, called Singularity, that covered endpoints, cloud workloads, and identity. It went after the same customers as CrowdStrike, its larger rival.

A One-Letter Ticker

SentinelOne priced its shares at $35 on June 29, 2021, above its range. The stock rose about 21 percent on its first day of trading. The company kept buying smaller firms. It paid $616.5 million for Attivo Networks in 2022 and in 2025 agreed to buy Prompt Security, which guards AI tools. Its losses narrowed as revenue grew, though the stock spent long stretches below the offer price. SentinelOne still trades on the NYSE under S.

Cover: On Guard, Antoine Auguste Ernest Hébert. Art Institute of Chicago, public domain. Chosen for a soldier on guard (the sentinel).