Be careful with RPMSG files
Not many people are aware of “.rpmsg” files. The file extension means “restricted-permission message”. They are used to deliver email messages between people and implement some controls applied at the recipient side. Such permissions are, by example, the right to forward or copy the original email. You may compare this to some kind of “DRM” (Digital Rights Management) for emails. RPMSG files are used inside a Microsoft ecosystem because they are created by users of Azure Information Protection, or Active Directory Rights Management Services[1]. The file is encrypted and only the recipient will be able to decrypt and open the message.
The good news for users, this is pretty transparent because Outlook will automatically open RPMSG files for you and display it. The are delivered as attachment with the following MIME type:
Content-Type: application/x-microsoft-rpmsg-message
I was aware of phishing campaigns that implement this type of file to deliver malicious content to the victim. Because RPMSG files are handled by Microsoft tools, the sender of the email must have a valid Microsoft account and be able to send messages to the potential victim. This means that such attacks are targeted and imply the use of a compromised account.
I did a retro-hunt on virustotal.com and searched for files containing this MIME-type and found 819 matches across the last 90 days. Most files were dump of email messages.
Why use RPMSG files? Probably to defeat most of the classic security controls and make the email trusted. The phishing content is stored inside the protected message. If you don't use RPMSG with 3rd party organizations on a regular basis, it could be interesting to have a look at such kind of messages...
Xavier Mertens (@xme)
Xameco
Senior ISC Handler - Freelance Cyber Security Consultant
PGP Key
Comments
www
Nov 17th 2022
6 months ago
EEW
Nov 17th 2022
6 months ago
qwq
Nov 17th 2022
6 months ago
mashood
Nov 17th 2022
6 months ago
isc.sans.edu
Nov 23rd 2022
6 months ago
isc.sans.edu
Nov 23rd 2022
6 months ago
isc.sans.edu
Dec 3rd 2022
5 months ago
isc.sans.edu
Dec 3rd 2022
5 months ago
<a hreaf="https://technolytical.com/">the social network</a> is described as follows because they respect your privacy and keep your data secure. The social networks are not interested in collecting data about you. They don't care about what you're doing, or what you like. They don't want to know who you talk to, or where you go.
<a hreaf="https://technolytical.com/">the social network</a> is not interested in collecting data about you. They don't care about what you're doing, or what you like. They don't want to know who you talk to, or where you go. The social networks only collect the minimum amount of information required for the service that they provide. Your personal information is kept private, and is never shared with other companies without your permission
isc.sans.edu
Dec 26th 2022
5 months ago
isc.sans.edu
Dec 26th 2022
5 months ago