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Attackers Use Passkey Phishing to Hijack Microsoft Cloud Accounts and Exfiltrate Data
Microsoft details two campaigns: million-email CEO impersonation ACH fraud and passkey-themed vishing that hijacks Microsoft cloud accounts for data theft and extortion.
Microsoft disclosed a campaign that sent over one million CEO-impersonation scam emails between August 3-5, 2026, targeting U.S. accounts payable departments with fake ServiceNow subscription invoices to induce ACH transfers, using generative AI to tailor templates. A second campaign detected since May 2026 uses passkey/MFA-themed voice phishing posing as the IT help desk, redirecting victims via SMS to counterfeit Microsoft sign-in pages and adversary-in-the-middle or device-code flows to hijack accounts. Post-compromise activity includes adding attacker-controlled authentication methods, high-volume Microsoft Graph activity, SharePoint and OneDrive downloads, and mailbox collection via REST APIs. Microsoft attributes initial access to Storm-3121 (linked to ShinyHunters and Falcon extortion) and Storm-3032 (UNC6671, a BlackFile splinter operating the Helix extortion brand).
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Passkey-themed phishing attacks lead to Microsoft 365 data theft
Microsoft links ShinyHunters- and Helix-affiliated actors to passkey-themed vishing and device-code phishing that compromises Microsoft 365 accounts and steals cloud data.
Microsoft attributes passkey- and SSO-themed social engineering activity, observed since May 2026, to Storm-3121 (linked to ShinyHunters and Falcon) and Storm-3032 (tied to BlackFile members now operating as Helix). Attackers impersonate corporate IT help desks by phone or SMS, urging fake passkey, MFA, or SSO updates and directing victims to adversary-in-the-middle phishing pages or device-code authentication flows that yield credentials, session tokens, and OAuth tokens. Post-compromise behavior includes Microsoft Graph enumeration of users, SharePoint, and OAuth grants, plus persistence via attacker-controlled MFA methods. Google Threat Intelligence tracks related activity as UNC6671, linked to the BlackFile, Helix, Falcon, Pink, and Redact extortion gangs.
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Hackers Pose as IT Support to Hijack Microsoft 365 Accounts With Fake Passkey Alerts
Microsoft warns of vishing campaigns by Storm-3121 and Storm-3032 hijacking Microsoft 365 accounts via fake passkey alerts, adding attacker-controlled MFA and exfiltrating cloud data.
Microsoft Security Research has tracked the campaign since May 2026: callers posing as IT helpdesk staff tell employees to urgently update passkeys, MFA, or SSO settings via domains such as add-passkey[.]com and contoso[.]add-passkey[.]com. The lures lead to adversary-in-the-middle phishing or device-code authentication flows that yield credentials, session tokens, or OAuth tokens, after which attackers enroll their own MFA methods for persistence and run Microsoft Graph reconnaissance. They then collect SharePoint, OneDrive, and sometimes Exchange Online data at deliberately low rates (often under 1,000 files or messages per hour), with python-httpx seen in high-volume file access. Microsoft attributes initial access tradecraft to Storm-3121 and Storm-3032, linked respectively to ShinyHunters/Falcon and BlackFile/Helix extortion operations.
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Protecting organizations from AI-assisted executive impersonation and invoice fraud
Microsoft tracked a campaign of over one million AI-crafted CEO-impersonation emails seeking ~$50,000 ACH payments with fabricated ServiceNow invoices.
Between August 3 and 5, Microsoft detected a campaign of more than one million fraud emails, 87.7% of them targeting US enterprise users, sent through multiple third-party email delivery service accounts. The actor impersonated CEOs, CFOs, and presidents of targeted companies, urging accounts payable staff to process an ACH payment of nearly $50,000. Lures layered executive impersonation, lookalike domains, a fabricated ServiceNow 'Annual Subscription' invoice personalized to the recipient, and forged forwarded email threads; Microsoft found no evidence ServiceNow or the referenced executives were compromised. Microsoft observed indicators consistent with generative AI-assisted template creation, while leftover inconsistencies such as missing forwarding headers and mismatched display names gave defenders detection cues.
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The Smishing Deluge: China-Based Campaign Flooding Global Text Messages
Unit 42 attributes a global smishing campaign with 194,000+ phishing domains impersonating tolls, banks, and couriers to the Smishing Triad.
Palo Alto Unit 42 attributes ongoing smishing texts about toll violations and package misdelivery to the Smishing Triad, targeting U.S. residents since April 2024. Researchers identified 194,345 FQDNs across 136,933 root domains registered since January 2024, mostly via Hong Kong registrar Dominet (HK) Limited with Chinese nameservers and hosting concentrated on U.S. cloud services. The decentralized campaign impersonates banking, cryptocurrency, e-commerce, healthcare, law enforcement, and social media services, and its scale points to a large phishing-as-a-service operation. Phishing pages harvest national ID numbers such as Social Security numbers, home addresses, payment details, and login credentials.
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BigBear 2.0 phishing campaign hijacks Microsoft 365 sessions after MFA
CloudSEK uncovered BigBear 2.0, a PhaaS operation that captured 4,148 Microsoft 365 session cookies, hijacking authenticated sessions after MFA via AiTM proxy.
CloudSEK infiltrated the BigBear 2.0 phishing-as-a-service panel in June, finding 5,137 credential records tied to 461 organizations in over 40 countries, including 4,148 captured session cookies and 474 completed post-MFA logins. The operation, built on Evilginx2, uses an attacker-controlled reverse proxy to steal authenticated session cookies and residential proxies to defeat location-based Conditional Access checks, while custom code disables FIDO2/WebAuthn on phishing pages. At least five affiliates operated 42 VPS nodes, with IT services and managed service providers the most targeted sector.
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