He went one layer deeper than everyone else - past the app, into the API. Then he taught a machine to guard it, alone.
The Dispatch
Yisi Gross does not sell fear. He sells plumbing. Specifically, the plumbing of the modern internet - the APIs, those quiet channels where one machine hands data to another, thousands of times a second, with no human watching. In 2015 that was a footnote. Gross treated the footnote like a headline, and built a company on the difference.
That company is ammune.ai, founded as L7 Defense with Dr. Doron Chema. The pitch was blunt: firewalls and hand-written rules cannot keep pace with attacks that mutate in real time. The only defense that scales is one that learns what normal traffic looks like, notices when something turns strange, and acts on its own. Unsupervised. Air-gapped. No analyst waiting to approve the block.
It sounds obvious now. It did not in 2015, when most security budgets still pointed at the perimeter and "API security" wasn't a line item anyone had heard of. Gross made the bet early and held it long enough for the market to arrive - and for ammune to land deployments across finance, telecom and SaaS on three continents.
By the numbers
The Build
There is a romantic version of the startup story where the technical genius invents something and the world beats a path to the door. The world does not do that. Someone has to carry the idea into rooms full of skeptical enterprise buyers, translate the math into a purchase order, and keep the lights on while the science matures. At L7 Defense, that someone was Gross.
His title kept shifting - co-founder, director, COO, VP of business development - because at a young company one person wears the whole thing. He ran the partnerships that gave the product reach: a tie-up with Niagara Networks to push zero-trust down to API communication, and an integration with NVIDIA's BlueField-2 data processing units that moved the AI defense right onto the network hardware.
The funding round in 2021 was the validation. TRUMPF Venture, the corporate arm of a German industrial giant, led it. Quick Heal, an Indian cybersecurity mainstay, joined. Two very different investors on two continents, agreeing that the boring problem was the important one.
In his words
"This funding round will enable us to further extend our technological leadership, to increase our international exposure and gain further market awareness."
Yisi Gross, on closing the Series A
The Route
The Second Act
These days Gross sits on the other side of the table. As Managing Partner at TYH Investments, alongside Meir Izralevich, he backs the kind of founder he used to be: technical, early, chasing a problem the market hasn't fully named yet.
Having built a company from footnote to funded, he can read a pitch for the thing it isn't saying. The operator's scar tissue is the investor's instinct.
Foundational over flashy. The markets without cameras - machine-to-machine trust, infrastructure, security plumbing - tend to age well.
Speaker, mentor, cyber-community organizer. He treats the ecosystem as something you tend, not just something you extract from.
Margins & Marginalia
His social handles trace a straight line through one obsession: l7defense on Twitter and Facebook, ammune on LinkedIn. The brand evolved; the mission didn't.
Ammune decides what to block without a human in the loop. Getting an enterprise to trust software that acts on its own is the real product - the algorithm is the easy part.
TYH Investments runs out of a Brooklyn address - a long way from the Jerusalem lecture halls where the MBA in marketing and finance began.
Sources: Crunchbase, Startup Nation Central, SourceSecurity, PR Newswire, TYH Investments, LinkedIn. Facts drawn from public records; where a claim could not be verified, it was left out.
Yisi Gross (Yisrael Gross) is an Israeli-rooted, New York-based technology entrepreneur and investor. He co-founded L7 Defense (now ammune.ai), an AI-driven API security company that raised Series A backing from TRUMPF Venture and Quick Heal, and today works as a Managing Partner at TYH Investments, backing early-stage high-tech startups. He built his reputation on the unglamorous frontier of API-borne attacks, arguing that autonomous, machine-learning defense - not human-tuned rules - is the only way to keep pace with modern cyberattacks.
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