Harmonic Security raises $50M to govern how employees use AI

Harmonic Security has closed an oversubscribed $50 million Series B round to build out what it calls workforce AI protection. Crosspoint Capital Partners led the round, and existing investors also participated.

The pitch is simple. Employees are pasting company information into AI tools, and security teams want to see it, and ideally stop the bad stuff, before it leaves the building.

The details of the round

The company announced the Series B on October 14, 2026. The new money lifts Harmonic’s total funding to $76 million.

Harmonic says the capital will go toward expanding its engineering and go-to-market teams. Headcount has already passed 90 employees, split across the US and the UK.

The startup was founded in 2023 and operates out of San Francisco and London.

For comparison, Harmonic completed a $17.5 million Series A in late 2024. The Series B is nearly three times that size.

On the customer side, Harmonic says its platform covers millions of employees at more than 100 enterprise customers. It has also signed distribution partnerships with Climb Global Solutions and Distology to widen its reach through the channel.

What the product actually does

Technically, the platform governs employee use of AI tools in real time. It inspects interactions as they happen and enforces controls based on what it finds.

To do that, Harmonic relies on custom small language models rather than giant general-purpose ones. These models classify the task an employee is attempting and detect sensitive data in the exchange.

Harmonic puts its latency at about 200 ms. The company also claims 96% fewer false positives than traditional data loss prevention systems.

The shadow AI problem

Harmonic is aiming squarely at “shadow AI” — employees using AI tools that their employer has not approved, or using approved tools in ways nobody is monitoring.

Harmonic says it can deliver security governance without the heavy lifting that traditional data classification usually requires, which typically asks organizations to label and sort their data before protections can work.

The founders are Alastair Paterson and Bryan Woolgar-O’Neil. Both come to Harmonic with prior track records in the cybersecurity sector. Paterson previously built and sold Digital Shadows, a company acquired for $160 million in 2022.

What this means for enterprises and the security market

The channel partnerships with Climb Global Solutions and Distology are worth watching. Distribution through resellers can accelerate adoption among companies that do not buy directly from startups, and it can help a young company compete against incumbents with established sales networks.