Case Study: Greenhill & Co. achieves zero missed email attacks and prevents BEC with Abnormal AI

Guiding Global Clients Securely Through Mergers, Restructuring, and More

Greenhill & Co., a global investment bank advising clients on mergers, restructuring, and financing, faced persistent, socially engineered email threats that bypassed its Microsoft Defender for Office 365 and gateway controls. As a high‑profile target handling sensitive transactions, Greenhill sought a solution that would keep realistic-looking spear phishing, invoice fraud, and account takeover attacks out of employees’ inboxes — so they turned to Abnormal AI.

Abnormal AI was integrated via API with Greenhill’s Microsoft 365 environment and ran a quick, invisible proof-of-value to baseline normal behavior using behavior‑based AI and VendorBase™ capabilities (plus Email Account Takeover Protection). Abnormal AI auto-remediated threats and freed the security team to focus on other projects, stopping 130+ BEC attacks, identifying 70+ compromised vendor accounts, blocking 7,000+ credential‑phishing emails and 11,000+ name‑impersonation attacks, and recording zero missed attacks in the past 16 months.

Greenhill & Co.

John Shaffer

CIO/Chief Information Security Officer