Harmonic Security, which sells software that polices how employees use AI tools at work, said Oct. 14 it raised a $50 million Series B led by Crosspoint Capital Partners, an oversubscribed round that brings its total funding to $76 million.
The company, founded in October 2023 and based in San Francisco and London, did not disclose its new valuation or name the other investors that joined the round. Its previous rounds included a $17.5 million Series A led by Next47 in October 2024 and a $7 million seed round led by Ten Eleven Ventures.
What the product does
Rather than blocking employees from using AI tools outright, Harmonic's platform is built to show companies which AI tools their staff are actually using, what data they are sharing with them and why, then apply controls in real time as the interaction happens. The company says it relies on small, custom-built language models, rather than large general-purpose ones, to classify what an employee is attempting within milliseconds and distinguish, for example, a harmless reference to a database structure from an accidental leak of live credentials. Coverage spans browser-based AI tools, desktop applications and, increasingly, autonomous AI agents. Harmonic says it now has customers across more than 100 companies and has grown headcount from roughly 30 a year ago to more than 90 employees across the U.S. and UK.
"Every board I talk to is asking two questions" about AI.
— Alastair Paterson, co-founder and chief executive, Harmonic Security
Mr. Paterson, who previously built and sold the threat-intelligence firm Digital Shadows to ReliaQuest for $160 million in 2022, pointed to pressure from boards to both guard against AI-related risk and capture its value. Crosspoint's Zach Sivertson said the firm backed the round because "security has too often slowed the adoption of new technology," a dynamic he said Harmonic's approach was designed to avoid.
A crowded, fast-moving market
The round lands in a sector that has drawn heavy acquisition interest: SentinelOne bought Prompt Security for a reported $250 million and Cato Networks agreed to acquire Aim Security for an estimated $300 million to $350 million, both this year. Gartner projects the broader AI security software market to grow from $15.6 billion in 2025 to $37.6 billion by 2030. Harmonic plans to use the new funding to expand engineering, sales and marketing teams in the U.S. and UK as it competes for enterprise customers racing to adopt AI tools faster than their security teams can track them.
