Security News > 2022 > October > Microsoft Office 365 email encryption could expose message content
Security researchers at WithSecure, previously F-Secure Business, found that it is possible to partially or fully infer the contents of encrypted messages sent through Microsoft Office 365 due to the use of a weak block cipher mode of operation.
Organizations use Office 365 Message Encryption to send or receive emails, both external and internal, to ensure confidentiality of the content from destination to source.
Harry Sintonen of WithSecure underlines that with Office 365 Message Encryption the content of the encrypted messages isn't directly decipherable, but structural information about those messages can be captured.
An attacker able to collect multiple encrypted messages can look for patterns that could lead to parts of the message to become gradually readable without the need of an encryption key.
To demonstrate that this can be achieved, Sintonen revealed the content of an image protected by Office 365 Message Encryption.
WithSecure recommends that until a more secure mode of operation becomes available, users and admins should stop using or trusting the Office 365 Message Encryption feature.
News URL
Related news
- Microsoft Office 2024 now available for Windows and macOS users (source)
- Microsoft 365 Admin portal abused to send sextortion emails (source)
- A Hacker's Era: Why Microsoft 365 Protection Reigns Supreme (source)
- Ransomware attackers hop from on-premises systems to cloud to compromise Microsoft 365 accounts (source)
- Microsoft fixes Outlook email sending issue for users with many folders (source)
- Over 5,000 Fake Microsoft Notifications Fueling Email Compromise Campaigns (source)
- New Mamba 2FA bypass service targets Microsoft 365 accounts (source)
- Microsoft Detects Growing Use of File Hosting Services in Business Email Compromise Attacks (source)
- Microsoft Outlook bug blocks email logins, causes app crashes (source)
- Microsoft says more ransomware stopped before reaching encryption (source)