Security News > 2023 > May > Microsoft 365 phishing attacks use encrypted RPMSG messages

Attackers are now using encrypted RPMSG attachments sent via compromised Microsoft 365 accounts to steal Microsoft credentials in targeted phishing attacks designed to evade detection by email security gateways.
RPMSG files are encrypted email message attachments created using Microsoft's Rights Management Services and offer an extra layer of protection to sensitive info by restricting access to authorized recipients.
"The recipients were users in the billing department of the recipient company. The message shows a Microsoft encrypted message."
The attackers' use of trusted cloud services such as Microsoft and Adobe to send phishing emails and host content adds an additional layer of complexity and trustworthiness.
Encrypted RPMSG attachments also conceal phishing messages from email scanning gateways, given that the only hyperlink in the initial phishing email directs the potential victims to a legitimate Microsoft service.
"To help prevent Microsoft 365 accounts being compromised, enable Multi-Factor Authentication."
News URL
Related news
- Hidden Threats: How Microsoft 365 Backups Store Risks for Future Attacks (source)
- Tycoon2FA phishing kit targets Microsoft 365 with new tricks (source)
- Microsoft links recent Microsoft 365 outage to buggy update (source)
- Hackers Exploit AWS Misconfigurations to Launch Phishing Attacks via SES and WorkMail (source)
- New ClickFix attack deploys Havoc C2 via Microsoft Sharepoint (source)
- New Microsoft 365 outage impacts Teams, causes call failures (source)
- YouTube warns of AI-generated video of its CEO used in phishing attacks (source)
- Microsoft 365 apps will prompt users to back up files in OneDrive (source)
- Microsoft Warns of ClickFix Phishing Campaign Targeting Hospitality Sector via Fake Booking[.]com Emails (source)
- Malicious Adobe, DocuSign OAuth apps target Microsoft 365 accounts (source)