Prompt Security

Primary category: dlp. Cross-listed in ai-runtime-security, ai-spm, and ai-access-governance. Acquired by sentinelone (2025).

One-liner — A GenAI security platform that gives enterprises visibility and control over employee and developer AI use — shadow-AI discovery, prompt-injection defense, and prompt/response DLP — now SentinelOne’s AI-security product.

What it does

Prompt Security inspects GenAI traffic in real time to enforce policy on both sides of the prompt: it blocks prompt injection and jailbreaks (untrusted input), redacts/prevents sensitive-data leakage into prompts and from responses (DLP), discovers shadow AI (which AI tools employees use), and governs AI agent behavior. Coverage spans browsers, desktop apps, and APIs, so it controls both workforce AI usage and homegrown AI applications.

Where it sits in the stack

It straddles several layers, which is why it’s cross-listed:

• dlp — prevents sensitive data leaving via prompts/responses.
• ai-runtime-security — inline AI firewall blocking prompt injection.
• ai-access-governance — CASB-for-AI shadow-AI discovery and policy over sanctioned/unsanctioned tools.
• ai-spm — inventory/posture of AI usage and agents. It lives in the yellow (AI application/usage) trust zone, screening untrusted input, preventing sensitive-data leakage, and controlling outbound data flows.

Deployment & architecture

Multi-channel enforcement: browser extension, desktop agent, and API/SDK/inline-proxy in front of models or AI gateways — i.e., it can govern SaaS AI usage and self-built apps without forcing all traffic through one network choke point. Integrates with IdP, SIEM/SOC, and AI gateways. Post-acquisition, capabilities are being integrated into sentinelone Singularity.

Positioning & differentiators

• Known for broad coverage across the “shadow AI + AI firewall + AI DLP” combination in one product, rather than specializing in only red-teaming or only guardrails.
• Nearest neighbors: witnessai, lasso-security, harmonic-security, aurascape (access governance); lakera, pangea, hiddenlayer, prisma-airs, cisco-ai-defense (runtime/guardrails).
• Strategic-investor signal: Okta and F5 backed it pre-acquisition.

Ownership, funding & M&A

Seed flag “acq by SentinelOne” — CONFIRMED and closed. sentinelone signed the merger agreement and announced the deal on 2025-08-05, and completed it on 2025-09-05 — confirmed twice in SentinelOne’s own SEC filings (Form 8-K filed 2025-09-08: the acquisition “was completed on September 5, 2025”; Q3 FY2026 Form 10-Q Note 4 repeats the same date). The announcement-day release was explicit that the deal was still pending, “subject to any applicable regulatory approvals and customary closing conditions,” so the two dates are genuinely a month apart.

On price, three numbers circulate and only two are sourced to SentinelOne: ~$180M (cash + Class A stock) is the deal value in the 8-K, and $159.3M is the GAAP purchase consideration in the 10-Q’s purchase-price allocation ($133.6M cash + $17.2M stock + $0.9M assumed options + $7.6M indemnity holdback), with the gap treated as post-combination compensation. The widely repeated ~$250M is a Calcalist/CTech press estimate that appears in no SentinelOne filing or release — treat it as unconfirmed. PPA also shows goodwill of $130.4M and $21.6M of intangibles ($20.0M developed technology, $1.6M customer relationships, both 2-year lives).

Pre-acquisition: founded August 2023 in Tel Aviv by Itamar Golan (CEO) and Lior Drihem (CTO), both ex-Unit 8200; ~$23M raised (Hetz Ventures, Jump Capital, Ridge Ventures, plus strategics Okta and F5) — a strong outcome for a two-year-old company. Confidence: high on the acquisition, dates and filed price figures.

Don’t conflate this with SentinelOne’s Observo, Inc. deal, signed 2025-09-08 and completed 2025-09-22 (~$225M per 8-K) — a separate acquisition in the same fiscal quarter.

CTO / hedge-fund lens

Day-1 for the AI-usage control problem: if employees are pasting into ChatGPT/Claude and you need shadow-AI visibility plus prompt DLP, this is exactly the control. Now that it’s part of SentinelOne, it’s most attractive to existing SentinelOne shops; others should still shortlist it but evaluate the platform-lock implications. Touches model-risk/data-governance posture but is not itself an SR 11-7 governance platform. Fits enterprise and mid-market.

Competitors / alternatives

witnessai, harmonic-security, lasso-security, aurascape, wald-ai, cyberhaven (access governance / AI DLP); lakera, pangea (now CrowdStrike), prisma-airs, cisco-ai-defense, hiddenlayer (runtime/guardrails).

Open questions / to verify

• Final purchase price and confirmed close date — RESOLVED 2026-07-27: closed 2025-09-05; ~$180M deal value / $159.3M GAAP purchase consideration per SentinelOne’s 8-K and 10-Q. The ~$250M press figure is unsupported by any filing.
• Whether it remains sold standalone or only within SentinelOne Singularity.

Sources

• SentinelOne Form 8-K (filed 2025-09-08) — fetched 2026-07-27 — supports: close date 2025-09-05 (“completed on September 5, 2025”), merger agreement dated 2025-08-05, ~$180M cash + Class A stock deal value; confidence: high (primary). Cached: raw/sources/2026-07-27--prompt-security--sentinelone-close-date.md
• SentinelOne Form 10-Q, quarter ended 2025-10-31 (filed 2025-12-04), Note 4 Acquisitions — fetched 2026-07-27 — supports: close date 2025-09-05 (independent corroboration), $159.3M purchase consideration breakdown, goodwill $130.4M, intangibles $21.6M; also separates the Observo deal (closed 2025-09-22) from Prompt; confidence: high (primary)
• SentinelOne to Acquire Prompt Security to Advance GenAI Security — fetched 2026-06-28, re-checked 2026-07-27 — supports: announcement date 2025-08-05, capabilities, and explicit pending language (“expected to close in … third quarter of fiscal year 2026 … subject to … customary closing conditions”); confidence: high
• SentinelOne buys Prompt for $250M (Calcalist) — fetched 2026-06-28 — supports: founded 2023, two years old; the ~$250M value is a press estimate contradicted by SentinelOne’s filings (see 8-K/10-Q above) — do not cite it as fact; confidence: low on price, med otherwise
• Prompt Security + SentinelOne: A New Chapter Begins (Prompt blog) — fetched 2026-06-28 — supports: founders, Tel Aviv HQ, deal narrative; confidence: med (vendor)

History

• [2026-06-28] Stub created from seed registry.
• [2026-06-28] Researched; CONFIRMED acquisition by SentinelOne (announced 2025-08-05, ~$250M cash+stock, closed fiscal Q3 FY2026) — raised ownership_confidence to high. Established founded Aug 2023, HQ Tel Aviv, founders Golan/Drihem, ~$23M raised (incl. Okta, F5). Kept the four cross-listed categories. Set hedge_fund_fit high.
• [2026-07-27] Date-sanity sweep — corrected a fabricated close date. closed was 2025-08-05, an exact copy of the announcement date, which the page’s own ownership_note contradicted by saying the deal “closed in SentinelOne fiscal Q3 FY2026” (a quarter ending 2025-10-31). Checked SentinelOne’s SEC filings: the Form 8-K filed 2025-09-08 states the acquisition “was completed on September 5, 2025”, and the Q3 FY2026 10-Q Note 4 independently repeats that date — so the real close is 2025-09-05, one month after announcement. Also replaced the null price with the two filed figures (~$180M deal value per the 8-K; $159.3M GAAP purchase consideration per the 10-Q PPA) and demoted the ~$250M Calcalist number to an explicitly unconfirmed press estimate, since it appears in no SentinelOne filing or release. ownership_state: acquired-closed confirmed correct and now genuinely sourced. Added a note distinguishing the separate Observo deal (closed 2025-09-22) that fell in the same quarter. Cached 1 new source.