Harmonic Security raises $50M Series B to secure employee AI use

Harmonic Security has raised a $50 million Series B led by Crosspoint Capital Partners, bringing its total funding to $76 million. The company didn’t say what valuation it got, and it said the round was oversubscribed and included existing investors. Next47 backed its $17.5 million Series A in October 2024, and Ten Eleven Ventures led the $7 million seed round the year before.

This is a familiar play for founder Alastair Paterson, who previously co-founded Digital Shadows and sold it to ReliaQuest for $160 million in 2022. He’s now building Harmonic with co-founder and CTO Bryan Woolgar-O’Neil, who also held the CTO role at Digital Shadows. Harmonic says the data and machine learning team came over too, and that the company was formed in October 2023 after talking to more than 50 security leaders.

The product is built around monitoring how employees use AI tools rather than shutting them off. Harmonic says its software shows which tools people use, what data they share, and why, while its small language models inspect interactions in milliseconds. The company says that lets it tell the difference between someone talking about a schema and someone copying live credentials. A Usage Intelligence layer also tries to show managers where AI is actually useful and where future investment might make sense.

Harmonic says its software is used by millions of employees across more than 100 companies, including large enterprises. The company’s team has grown from 30 people in October 2024 to more than 90 across the US and the UK, and the new money will go into engineering, sales, and marketing in both places. That expansion comes as Prompt Security and Aim Security have already been bought, and as larger security vendors keep circling the AI-security market.

The company’s pitch is simple: don’t make employees choose between speed and control. That’s smart, and probably overdue. Security products that only say “no” tend to lose to the tools people want anyway; the real race is who can put guardrails on AI without turning the office into a locked filing cabinet.