Fake Calendar Invites Steal Microsoft Logins

Check Point Research · Medium sophistication
Last updated October 19, 2026

Check Point researchers identified a large credential-phishing campaign that used counterfeit calendar invitations to send people to fake Microsoft sign-in pages. The campaign used calendar attachments and deceptive meeting links, and targeted more than 40,000 organizations with over 302,000 phishing emails.

Key findings

  • Counterfeit calendar invitations were used to direct recipients to credential-harvesting pages.
  • The invitations contained either calendar attachments or deceptive meeting links.
  • Researchers identified more than 302,000 unique phishing emails targeting over 40,000 organizations.

Who’s being targeted

  • Commonly targeted roles: All employees, Executive assistants, Administrative staff, Executives, Microsoft 365 users.
  • Affected industries: Multiple industries.
  • Attack channels: email.
  • Impersonated: Microsoft meeting or calendar service.

Awareness takeaways

  • Treat unexpected calendar invitations like other suspicious messages: confirm the organizer and purpose before opening an attachment or following a meeting link.
  • Do not enter Microsoft credentials after following an unexpected meeting link; instead, navigate to Microsoft services using a known bookmark or trusted application.
  • Train all staff, not only technical teams, to recognize calendar invitations as a potential phishing delivery method.

Red flags to watch for

  • An unexpected calendar invitation or meeting request.
  • A meeting link sends the user to a sign-in page instead of a normal meeting page.
  • The invitation asks for Microsoft credentials when the user did not expect to reauthenticate.
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Read the video transcript

That unexpected meeting invite? It could be a Microsoft login trap. It says, ‘You have been invited to a meeting.’ Open the calendar attachment or click the meeting link, and a fake Microsoft sign-in page asks for your password. Here’s the giveaway: you expected meeting details, not a login. Check Point found over 302,000 phishing emails targeting more than 40,000 organizations. Unexpected invite asking you to sign in? Skip that link. Open your trusted calendar app to check the meeting.

MITRE ATT&CK techniques

T1566.002 - Phishing: Spearphishing Link · PhishingT1566.001 - Phishing: Spearphishing Attachment · PhishingT1204.001 - User Execution: Malicious Link · User ExecutionT1204.002 - User Execution: Malicious File · User ExecutionT1056.003 - Input Capture: Web Portal Capture

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