What Is Abnormal AI?
Abnormal AI, Inc., which operated as Abnormal Security until April 2025, is a private cybersecurity company that uses behavioral AI to stop attacks aimed at people: phishing, business email compromise, vendor invoice fraud and account takeovers. Evan Reiser and Sanjay Jeyakumar founded it in 2018. The company lists its principal place of business in Las Vegas, Nevada, and Reiser has been CEO since the start.
Abnormal's core product connects to Microsoft 365 or Google Workspace through the providers' APIs. It builds a baseline of how each person normally emails, signs in and communicates, then flags and removes activity that deviates from that baseline. Because it does not sit in the mail flow, customers do not need to change MX records to deploy it.
Founding and Early Years
Reiser and Jeyakumar both came from TellApart, an advertising technology company that Twitter acquired. Reiser had co-founded AdStack, which TellApart bought, and earlier Bloomspot, which JPMorgan Chase bought; at Twitter he led product management and machine learning teams for the advertising business. Jeyakumar was a founding engineer at TellApart and later Twitter's systems architect for distributed data processing and machine learning, after working as a lead engineer at Google.
The two started the company in late 2018 at Greylock's offices. It was first called Abnormal AI, but the founders switched to Abnormal Security because, as Reiser later wrote, the security market did not yet take AI-named companies seriously. Abnormal came out of stealth in November 2019 with a $24 million Series A led by Greylock.
Funding, Valuation and ARR
Abnormal has raised four priced rounds. Menlo Ventures led a $50 million Series B in November 2020, after the company tripled its annual recurring revenue that year; Forbes reported a valuation above $500 million. Insight Partners led a $210 million Series C in May 2022 at a $4 billion valuation, following a year in which ARR tripled and headcount doubled. Wellington Management led a $250 million Series D in August 2024 at a $5.1 billion valuation, with Greylock, Menlo, Insight and CrowdStrike Falcon Fund participating. Total expected proceeds reached $546 million.
The company announced that ARR passed $100 million in August 2023 and $200 million in August 2024, when it said ARR was still growing more than 100% a year. These are company-reported figures; Abnormal does not publish audited financials. Reuters reported in 2023 that it was not yet profitable, and that it had hired former Forescout CEO Michael DeCesare as president.
Customers
Abnormal's customer count has grown from more than 1,300 in August 2023 (Reuters named Xerox, Mattel and Domino's) to more than 2,400 in August 2024, more than 3,200 in April 2025 and more than 4,500 in 2026. Its share of the Fortune 500 rose from 17% in August 2024 to 30% in September 2026, according to company announcements. In April 2025 it said three-fourths of its customers had moved away from a third-party secure email gateway.
Products
Inbound Email Security remains the main product. Around it Abnormal sells account takeover detection, AI Phishing Coach (personalized security training built from real attacks) and AI Data Analyst (automated reporting), both launched in April 2025, along with Email DLP rules added in 2026. Protection also covers cloud applications such as Slack, Workday, ServiceNow and Zoom.
In 2026 Abnormal pushed further beyond email. It described Attune 1.0, a behavioral foundation model trained on more than one billion derived behavioral signals; launched Identity Threat Protection, AI Governance and Infiltration Prevention in July; and in September added AI Employee Guardrails, AI Agent Security and AI Security Workbench to an AI Security suite that also includes AI Cloud Security, which uses OpenAI Daybreak models for investigation.
Rebrand, Public Sector and International Expansion
On April 16, 2025, the company returned to its original name, Abnormal AI, and changed its legal name from Abnormal Security Corporation to Abnormal AI, Inc. The same month it achieved FedRAMP Moderate authorization, 256 days after starting, and expanded operations into Germany. It added GovRAMP Moderate authorization in September 2025 and said in August 2026 that it was pursuing FedRAMP High.
Abnormal has operated in Japan since 2025, and SoftBank Corp. began reselling its email security platform to Japanese enterprises in September 2026. In August 2026 Abnormal and OpenAI announced a partnership under which Abnormal expands its use of OpenAI and joins the OpenAI Daybreak cyber partner program.
Competition and Risks
Abnormal competes with Microsoft Defender for Office 365, which is included in Microsoft 365 licenses, and with email security vendors such as Proofpoint and Mimecast. As it moves into identity and AI security it also meets larger platforms such as CrowdStrike and Okta. Its core product depends on access to Microsoft 365 and Google Workspace APIs. In July 2026 Anthropic sued Abnormal, alleging that the logo introduced with the 2025 rebrand copies Anthropic's branding.
Wellington said in 2024 that Abnormal had set its sights on the public market, and Reiser told Reuters in 2023 that the company was preparing to be a public company. As of September 2026 no IPO had been announced.
