Description

According to reports, threat actors are leveraging hijacked Microsoft 365 accounts to send malware encrypted RPMSG (restricted permission message files) attachments in order to steal Microsoft credentials without being noticed by email security gateways in a new phishing attempt. RPMSG files are encrypted email message files generated with Microsoft's Rights Management Service to add extra levels of protection to sensitive information. Threat actors used a hacked Talus Pay Microsoft 365 account to send emails to corporate billing department users containing a Microsoft encrypted message and demanding targets click on the "Read the message" button to open and decode the protected content. Instead, when clicked, it takes the recipient to a real Office 365 page where they must sign in with their Microsoft account. After authenticating using a real Microsoft service, recipients receive the attackers' phishing email, with the "Click here to Continue" button redirecting them to a fraudulent SharePoint document housed on Adobe's InDesign service. When targets click on a "Click Here to View Document" link, they are directed to an empty page with the message "Loading...Wait" in the title bar, which serves as a decoy for a malicious script to collect various information such as visitor ID, connect token and hash, video card renderer info, system language, device memory, hardware concurrency, installed browser plugin details, browser window details, and OS architecture. Finally, a cloned Microsoft 365 login page appears, encouraging users to submit usernames and passwords, which are subsequently sent to attacker-controlled servers. Furthermore, researchers argue that using trustworthy Microsoft and Adobe software makes detecting phishing emails and host material harder, adding another degree of complexity and trustworthiness.