The archive · AI & Models · Strategic decision · 2021–2024
Robust Intelligence bets AI needs a firewall; Cisco buys it for ~$400M as AI Act lands
Harvard professor's AI-firewall startup raised ~$40M, then sold to Cisco for a reported $400M as EU AI rules made model validation urgent.
Robust Intelligence
What the business is
Builds an AI firewall that automatically tests and protects models across their lifecycle against prompt injection, data poisoning, jailbreaks and other failure modes.
Starting capital：~$40M across two rounds from Sequoia, Tiger Global and others, plus a $5M strategic investment from Cisco
How it started
Founded in 2021 by Harvard professor Yaron Singer, who gave up tenure to protect AI from critical mistakes; built automated validation that detects model vulnerabilities; Sequoia became the largest investor, with Tiger Global also backing it, raising ~$40M in two rounds.
What happened
Cisco invested $5M a year before the exit; by mid-2024 Robust had ~$10M annual revenue and 70 employees, with major banks among customers; the EU AI Act formally took effect on 1 Aug 2024; Cisco announced its intent to acquire Robust on 26 Aug 2024, with US reports valuing the deal around $400M; the acquisition was completed on 24 Sep 2024.
How it ended up
Acquired by Cisco — announced 26 Aug 2024, completed 24 Sep 2024; founder Yaron Singer joined Cisco as a senior executive, and the technology became Cisco's security-for-AI line within the Cisco Security Cloud.
Background
Robust Intelligence built a firewall for AI: automated software that tests models for prompt injection, data poisoning, jailbreaks and other failure modes, from development through production. Founded in 2021 by Harvard professor Yaron Singer — who gave up tenure to start it — the company raised about $40M across two rounds, with Sequoia as its largest investor and Tiger Global also on the cap table.
The bet was that AI applications would face the same security scrutiny as software, and that regulators would force the issue. The EU AI Act formally took effect on 1 August 2024, phasing in obligations on AI providers, and Cisco — which had already invested $5M — announced its intent to acquire Robust on 26 August 2024, with US reports valuing the deal near $400M. By then Robust had roughly $10M in annual revenue and 70 employees, with major banks among its customers.
The deal closed on 24 September 2024; Singer joined Cisco as a senior executive and the technology became Cisco's security-for-AI offering inside the Cisco Security Cloud. It was a quiet exit — Cisco announced it by blog, not press release — but it made the founders' bet concrete: AI security became a line item the moment AI became regulated.
What has to be true
- The EU AI Act turned model validation from good practice into compliance, which is why the category got acquired the month it took effect.
- Automated testing, not consultants, was the only scalable way to secure models, which is why Cisco bought the product rather than building it.
- A reported $400M exit on ~$10M revenue shows buyers paid for the regulatory position, not the current P&L.
- Selling to banks first proved the market existed before regulation arrived, so the law only accelerated demand.
What can be applied
When a startup's bet is that a risk becomes regulated, the regulator's timetable can become its exit calendar — incumbents buy the category leader as rules take effect, so build the category first.
Aftermath
As of September 2026 Robust Intelligence no longer operates as an independent company: the acquisition by Cisco was completed on 24 September 2024 and its AI-validation technology was folded into the Cisco Security Cloud, where it anchors Cisco's security-for-AI product line. Founder Yaron Singer stayed on as a senior Cisco executive.
Sources
- Inside Yaron Singer's surprising $400M sale to Cisco
- Fortifying the future of Security for AI: Cisco Announces intent to acquire Robust Intelligence
- The European Union's world-first artificial intelligence rules are officially taking effect
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