INTRODUCTION:

Identified by Proofpoint as the threat actor behind the Contact Forms campaign, TA578 also appears to be pushing ISO files for Bumblebee malware through thread-hijacked emails.  These threat-hijacked emails either have links to storage.googleapis.com URLs similar to those used in the Contact Forms campaign, or they have password-protected zip attachments.  Either method delivers an ISO file containing files to install Bumblebee malware.

Today's diary compares two examples of ISO files for Bumblebee malware from Monday 2022-05-09 that appear to be from TA578.

Shown above:  Infection chains from TA578 on Monday 2022-05-09.

INFECTION CHAIN COMPARISON: LINK TO 'DOCUMENT' DOWNLOAD PAGE:

Shown above:  TA578 Thread-hijacked email with malicious storage.googleapis.com link.

Shown above:  TA578 'document' download page hosted on storage.googleapis.com URL delivers malicious ISO file for Bumblebee malware.

Shown above:  Contents of downloaded document.iso file.

INFECTION CHAIN COMPARISON: PASSWORD-PROTECTED ZIP ATTACHMENT:

Shown above:  TA578 email with password-protected zip attachment.

Shown above:  Malicious ISO file for Bumblebee malware extracted from password-protected zip attachment.

ISO FILE COMPARISON:

SHA256 hash: 330b01256efe185fc3846b6b1903f61e1582b5a5127b386d0542d7a49894d0c2

• File size: 2,883,584 bytes
• File name: document.iso
• File description: malicious ISO file sent by 'documents' download page

SHA256 hash: e9084037805a918e00ac406cf99d7224c6e63f72eca3babc014b34863fb81949

• File size: 2,883,584 bytes
• File name: invoice_pdf_49.iso
• File description: malicious ISO file extracted from password-protected zip attachment

ISO CONTENT COMPARISON:

SHA256 hash: 22e033c76bb1070953325f58caeeb5c346eca830033ffa7238fb1e4196b8a1b9

• File size: 1,612 bytes
• File name: documents.lnk
• File description: Windows shortcut in both document.iso and invoice_pdf_49.iso
• Shortcut: %windir%\system32\rundll32.exe ramest.dll,SjVjlixjPb

SHA256 hash: e6357f7383b160810ad0abb5a73cfc13a17f4b8ea66d6d1c7117dbcbcf1e9e0f

• File size: 1,390,592 bytes
• File name: ramest.dll
• File description: Bumblebee 64-bit DLL in document.iso

SHA256 hash: f398740233f7821184618c6c1b41bc7f41da5f2dbde75bbd2f06fc1db70f9130

• File size: 1,3900,80 bytes
• File name: ramest.dll
• File description: Bumblebee 64-bit DLL in invoice_pdf_49.iso

Note: Both of the above ramest.dll files have the same import hash (imphash) of 66356a654249c4824378b1a70e7cc1e5

SIMILARITIES TO CONTACT FORMS CAMPAIGN:

TA578 'document' download pages are similar to 'Stolen Images Evidence' pages used for the Contact Forms campaign.  Both are hosted on storage.googleapis.com pages with appspot.com in the URL.  Both generate traffic to a malicious URL ending in logo.jpg that returns script with base64 text used to generate a malicious ISO file for download.

The following are 4 examples of URLs generated by 'document' download pages for malicious ISO files in May 2022:

• hxxps://baronrtal[.]com/img/logo.jpg
• hxxps://bunadist[.]com/img/logo.jpg
• hxxps://omnimature[.]com/img/logo.jpg
• hxxps://vorkinal[.]com/img/logo.jpg

The following are 4 examples of URLs generated by 'Stolen Images Evidence' pages for malicious ISO files in May 2022:

• hxxps://bunadist[.]com/images/logo.jpg
• hxxps://curanao[.]com/images/logo.jpg
• hxxps://goranism[.]com/images/logo.jpg
• hxxps://olodaris[.]com/images/logo.jpg

As seen above, 'Stolen Images Evidence' pages generate URLs ending in /images/logo.jpg, while 'document' download pages generate URLs ending in /img/logo.jpg.

URLs hosted on storage.googleapis.com for 'Stolen Images Evidence' pages end with ?l= or ?h= or similar strings ollowed by a numeric value.  For example, hxxps://storage.googleapis[.]com/oieqeh1cxwnd81.appspot.com/bl/file/sh/0/fWpa4HT4ck6v6.html?l=827470894993112750 is a URL for a recent 'Stolen Images Evidence' page.

URLs hosted on storage.googleapis.com for 'document' download pages end in .html.  For example: hxxps://storage.googleapis[.]com/pz3ksj5t45tg4t.appspot.com/q/pub/file/0/filejBWdkst6Ua3s.html is a URL for a recent 'document' download page.

FINAL WORDS:

The Contact Forms campaign switches between pushing ISO files for Bumblebee malware, or pushing ISO files for IcedID (Bokbot) malware, and I've seen both during the same week.  Since February 2022, TA578 has been noted pushing both families of malware.  And in recent weeks, TA578 has been using thread-hijacked emails to distribute ISO files for Bumblebee malware.  TA578 might also distribute IcedID using the same type of thread-hijacked messages.

While the malware may be different, I occasionally find Cobalt Strike from either Bumblebee or IcedID when testing samples in Active Directory (AD) environments.  Cobalt Strike can lead to ransomware or other malicious activity.

If TA578 activity is caught and stopped in its early stages, potential victims might avoid more serious harm.

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Brad Duncan
brad [at] malware-traffic-analysis.net