Hackers Drops New Emotet Malware to Perform Mass Email Exfiltration From Victims Email Client

Emotet Malware re-emerging to perform mass email exfiltration with a new form of infection capabilities to steal sensitive Email data directly from victims Email Client.

The US-Cert team already issued an alert for an advanced Emotet malware attack that targets governments, private and public sectors in the most destructive way to steal various sensitive information.

The new Emotet malware campaign emerged again with a new module that capable of exfiltrating email content and send back to the attackers.

Also, it has some interesting new capabilities with this new campaign that enables email capture, examine the exfiltration process, and observe its global distribution.

Emotet Malware already caused very serious damage and it affected many countries,  U.S is one of the countries targeted by Emotet that made a huge damage in both government and private networks.

Emotet Malware Email Harvesting Process

Unlike old Emotet malware that steals contact list using  Outlook Messaging API, this new campaign used an API interface that gives an application access to email.

Old Emotet malware checks the configuration module of the email client especially the  registry key HKLM\Software\Clients\Mail\Microsoft Outlookto exfiltrate the Email data.

According to kryptoslogic, The new module, however, is more thorough, and also includes email subjects and bodies. It will crawl every email of every subfolder in the interpersonal message (IPM) root folder, and Perform the following actions

• Verify whether the email has been sent/received (PR_MESSAGE_DELIVERY_TIME) in the last 100e-9 * 15552000000 * 10000 / 3600 / 24 = 180 days;
• If so, obtain its sender (PR_SENDER_NAME_W, PR_SENDER_EMAIL_ADDRESS_W), destination (PR_RECEIVED_BY_NAME_W, PR_RECEIVED_BY_EMAIL_ADDRESS_W), subject (PR_SUBJECT_W) and body (PR_BODY_W).
• If the body is longer than 16384 characters, it is truncated to this size plus the string ....

Later on this Harvesting process, A DLL module drops by Emotet from the C2 server that injects payload binary into a new Emotet process.

Later it scans all the emails in the compromised email clients & saves the results to a temporary file and wait for this new DLL for the payload to finish the process else it kills after 300 seconds.

If the saved temporary file is bigger than  116 bytes then Original DLL issues an HTTP request using the WinINet API that helps to send the temporary file to the attacker via the C2 server.

“While Emotet’s operators may have simply moved to server-side extraction, harvesting data in mass provides a weaponized data-driven analytical capability which should not be underestimated, given how effective surgical email leaks have been in the recent past. ” Researchers said.