Calendar phishing represents an emerging cybersecurity threat that exploits the automatic acceptance features of calendar applications such as Google Calendar. According to threat detection engineers and cybersecurity analysts, this attack method has experienced rapid growth in recent months.
The scam operates by sending calendar invitations via email to work or personal addresses. A key advantage for fraudsters is that calendar applications can automatically add these invitations without requiring users to actively accept them, meaning the malicious entries appear in calendars even if recipients never open the corresponding emails or if messages land in spam folders. The fraudulent calendar entries then gain credibility by appearing alongside legitimate appointments, creating what security professionals describe as “borrowed credibility” that makes users more likely to engage with them compared to unsolicited emails.
Scammers employ various pretexts for these calendar invitations, including fake meetings, voicemail notifications, payment confirmations, and software renewal prompts. The calendar event descriptions typically contain either links directing users to fake login pages for services like Microsoft, Google, or PayPal, or phone numbers for fraudulent support lines. Some attackers increase the appearance of legitimacy by using legitimate platforms such as Zoom to send invitations or by customizing invitations to resemble internal company communications.
The sophistication of calendar phishing presents challenges for security defenses. Traditional email filtering systems struggle to block these invitations effectively, as filtering them out entirely would also prevent legitimate meeting requests from coming through. AI-powered security tools similarly face difficulties in distinguishing fraudulent from genuine calendar entries.
Security experts recommend treating unexpected calendar invitations with the same skepticism applied to suspicious emails. Rather than clicking links or declining invitations, users should delete or report them as spam. Additionally, users can adjust calendar settings to accept invitations only from known senders or only when explicitly accepted by the recipient.
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