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Harmonic Security raises $50 million while two of its rivals go to larger buyers

Harmonic Security raised a $50 million Series B led by Crosspoint Capital Partners, lifting its total funding to $76 million. Calcalist put rival Prompt Security's sale at about $250 million on $23 million raised, the nearest price comparison.

The Investor · Invest desk

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Prompt Security sold for far more than it raised Prompt Security's sale price as a multiple of its funding, its reported sale price, and Harmonic's total funding to date.

Prompt Security's reported sale price was about 10.9 times the capital it had raised. Calcalist put SentinelOne's purchase of Prompt Security at around $250 million. Harmonic's total funding has reached $76 million.

Prompt Security sold for far more than it raised
FigureValueNoteClaim
Prompt Security sale price vs. capital raised10.9 times, about16
Prompt Security sale price, per Calcalist$250 million aroundBuyer: SentinelOne12
Harmonic total funding$76 million2

What happened

  • Cato Networks has agreed to buy Aim Security, the second of Harmonic's competitors to go to a larger security company.
  • Harmonic called the round oversubscribed and said existing investors took part, but it did not name them or give a valuation.
  • Next47 led Harmonic's $17.5 million Series A in October 2024, and Ten Eleven Ventures led a $7 million seed round the year before.
  • Harmonic will spend the new money on engineering, sales and marketing in both the US and the UK.

Why it matters

  • What it sets up precedent Any later offer for Harmonic or a similar vendor will be measured against Prompt Security's reported sale price per dollar of capital raised.
  • What doesn't add up contradiction Harmonic's stated $76 million total is $1.5 million above its three named rounds, which sum to $74.5 million.
  • Who has to decide decision Security teams buying employee-AI-use monitoring have to weigh who will own the vendor: Prompt Security now sits inside SentinelOne and Aim Security is headed into Cato Networks.

Harmonic did not disclose a valuation [11], so the only price in this category is Prompt Security's, and it works out to 10.9 times the capital that company raised [16]. Put the same ratio on the $76 million Harmonic has raised [2] and the answer is about $826 million [18]. The ratio ignores revenue and burn, so it is not an estimate of what Crosspoint paid.

Anthropic's integrations are the counterweight to a sale story. Anthropic launched Compliance API integrations on May 21, 2026 with 28 security partners, among them Cloudflare, CrowdStrike, Netskope, Palo Alto Networks and Zscaler, and later stated the number had exceeded 100 [5]. Tech Funding News wrote that Harmonic is not the only company with that kind of access to enterprise AI use [10]. We'd expect a buyer that can see part of the same traffic through a partner integration to pay less for a standalone monitor.

Alastair Paterson, Harmonic's chief executive, said: "Every board I talk to is asking two questions: how do we reduce the risk of AI use and are we getting value?" [8] The second question is the one Harmonic's Usage Intelligence layer targets, according to the company: it helps managers identify valuable AI use cases and plan future investments [9]. We'd expect a security platform to find that harder to bundle than a monitor, though it is also the claim we can least check.

Our view is that the round buys Harmonic more time as an independent company. Headcount has at least tripled, from 30 people in October 2024 to more than 90 [15], and SecurityBrief UK reported about 100 new customers in 2026, with the annual target met in September [17].

The counter-thesis is in the same facts. Paterson has sold a founder-led company before, Digital Shadows to ReliaQuest for $160 million in July 2022 [4], and growth like this is what makes a company worth buying. SentinelOne has bought one rival and Cato Networks has agreed to buy another [12][13]. We would be wrong if Harmonic sells before it raises again.

Cato's price for Aim Security would show whether Prompt's 10.9 times is a pattern or a one-off.

What to watch

  • Cato's price for Aim Security, set against Prompt's 10.9 times capital raised.
  • Whether Harmonic discloses a valuation or investor names, or raises a Series C before any sale.
  • Whether the Anthropic compliance partner list, already past 100, adds vendors that package AI-usage monitoring.

Information, not investment advice. This story is general information about companies and markets, drawn from cited reporting. It is not a recommendation to buy, sell or hold any security; check the cited sources before acting.

Clarity's read

What the record supports and how the coverage leans. The claims behind it follow.

Reality

Evidence55
Adoption35
Hype gap+20
Incentives65
Confidence62

Perspective Coverage

6 publishers
Builder
Builder 27%
Operator
Operator 38%
Investor
Investor 35%
Why these scores

Claim ledger

Ranked by verification strength, evidence, and original report placement.

  1. [1]

    Harmonic Security raised a $50 million Series B round led by Crosspoint Capital Partners.

    Reported SupportedView cited source
  2. [2]

    Harmonic's total funding has now reached $76 million.

    Reported SupportedView cited source
  3. [3]

    Next47 led Harmonic's $17.5 million Series A in October 2024, and Ten Eleven Ventures led the $7 million seed round the year before.

    Reported SupportedView cited source
  4. [4]

    Alastair Paterson, Harmonic's CEO, co-founded the threat-intelligence firm Digital Shadows, which he sold to ReliaQuest for $160 million in July 2022.

    Reported SupportedView cited source
  5. [5]

    Anthropic launched Compliance API integrations on May 21, 2026 with 28 security partners, including Cloudflare, CrowdStrike, Netskope, Palo Alto Networks and Zscaler, and later stated that the number had exceeded 100.

    Reported SupportedView cited source
  6. [6]

    Harmonic's team grew from 30 people in October 2024 to more than 90 in the US and the UK.

    Reported SupportedView cited source
  7. [7]

    Harmonic will invest the new funding in engineering, sales and marketing in both the US and the UK.

    Reported SupportedView cited source
  8. [8]

    Alastair Paterson, Harmonic's chief executive and co-founder, said: "Every board I talk to is asking two questions: how do we reduce the risk of AI use and are we getting value?"

    Reported Supported Source: Alastair Paterson, Harmonic CEOView cited source
  9. [9]

    Harmonic states that its Usage Intelligence layer uses the same small-language-model technology to help managers identify valuable AI use cases and plan future investments.

    Reported Supported Source: Harmonic SecurityView cited source
  10. [10]

    Tech Funding News wrote that Harmonic is not the only company with access to enterprise AI use, and cited Anthropic's Compliance API integrations.

    Reported Supported Source: Tech Funding NewsView cited source
  11. [11]

    Harmonic said the Series B was oversubscribed and involved existing investors, but it did not disclose their names or the company's valuation.

    Reported Supported Source: Harmonic Security, as reported by Tech Funding NewsView cited source
  12. [12]

    SentinelOne acquired Prompt Security, a company that had raised $23 million, in a transaction that Calcalist put at around $250 million.

    Reported Supported Source: Calcalist, as reported by Tech Funding NewsView cited source
  13. [13]

    Cato Networks has agreed to purchase Aim Security, another competitor of Harmonic.

    Reported SupportedView cited source
  14. [14]

    Harmonic's three named rounds sum to $74.5 million, which is $1.5 million below the stated $76 million total.

    Derived Supported
  15. [15]

    Harmonic's headcount has at least tripled since October 2024.

    Derived Supported
  16. [16]

    Prompt Security's reported sale price was about 10.9 times the capital it had raised.

    Derived Supported
  17. [17]

    According to SecurityBrief UK, Harmonic acquired around 100 customers in 2026 and reached its annual target in September.

    Reported Insufficient Source: SecurityBrief UK, as reported by Tech Funding NewsView cited source
  18. [18]

    Applying Prompt Security's sale multiple to Harmonic's $76 million raised gives roughly $826 million, an illustration and not a valuation.

    Derived Insufficient

Sources

6 independent publishers whose own reporting we read for this story.

  1. cryptobriefing.com

    1 article · October 14, 2026

    Harmonic Security raises $50M to govern how employees use AI
  2. fintech.global

    1 article · October 15, 2026

    Harmonic Security bags $50m as boards demand AI proof
  3. scworld.com

    1 article · October 15, 2026

    Harmonic Security raises $50 million to govern employee AI tool usage
  4. securityweek.com

    1 article · October 14, 2026

    Harmonic Security Raises $50 Million for Workforce AI Protection
  5. techfundingnews.com

    1 article · October 14, 2026

    Harmonic Security raises $50M Series B to secure employee AI use — TFN
  6. ventureburn.com

    1 article · October 14, 2026

    Harmonic Security Raises $50M for AI Security Growth.

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