Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 29a2c70cd25944f3…

MALICIOUS

Office (OOXML)

101.2 KB Created: 2021-02-03 15:28:44 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2021-06-04
MD5: ba50b185523f27553a482c28ae44caf1 SHA-1: b56828615d6de020248ab9cc6c3889efb02d27e9 SHA-256: 29a2c70cd25944f3e22b4ec5d693f0389bee9884fd87701c52ff2c3d8ff6dfdc
184 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1204.002 Malicious File

The file contains Excel 4.0 macros, which are disguised and reassembled from split formulas. These macros are designed to download and execute a second-stage payload from the URL https://www.vukolider.com/soft.dll using regsvr32. The use of XLM macros and the payload download mechanism suggest a downloader or initial access stage.

Heuristics 5

  • Excel 4.0 macro sheet (1 sheet(s)) critical 3 related findings OOXML_XLM_MACROSHEET
    Spreadsheet contains an Excel 4.0 (XLM) macro sheet — XLM was a major Office malware vector during 2020-2022 and evaded many VBA-focused controls before Microsoft tightened XLM defaults. Even legitimate XLM use is rare in modern workbooks. The macro sheet is stored as XLSB/BIFF12 binary content, which many XML-only OOXML scanners miss.
  • Excel 4.0 macro sheet stored under disguised package path critical OOXML_XLM_DISGUISED_RELATIONSHIP
    OOXML package declares an xlMacrosheet relationship whose target is outside the canonical xl/macrosheets/ path. Excel follows the relationship type, while path-only scanners can miss the macro execution surface.
  • XLM payload reassembled from CHAR()/split formulas critical OOXML_XLM_REASSEMBLED_PAYLOAD
    An Excel 4.0 macro sheet builds its payload inside the formula token stream by concatenating per-character CHAR() calls and string fragments, so no WinAPI name, shell command, or URL is ever contiguous in the .bin for a literal-bytes scan to find. Reassembling the formulas recovered download/execute API names, LOLBin commands (regsvr32/rundll32/mshta/wmic/powershell), or a payload URL — the de-obfuscated download-and-run kill chain.
  • XLM payload URL string (1 URL) info OOXML_XLM_PAYLOAD_URL
    An Excel 4.0 (XLM) macro-sheet workbook with download/execute evidence carries a literal http(s) URL stored as a (often UTF-16) string in the shared-string table or a cell. This is the next-stage payload host referenced by the macro download chain (URLDownloadToFile/ShellExecute); surfaced as an IOC.
  • Embedded URL info EMBEDDED_URL
    One or more URLs were extracted from the document. The URL itself is not a detection — see the per-URL labels for which channel (macro, JS, link annotation, document body, ...) reached each URL.
    URL https://www.vukolider.com/soft.dll Referenced by macro

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin xlm-macrosheet OOXML XLM macro sheet: xl/dpo/sheet1.bin 959417 bytes
SHA-256: 438fad621ee310698a19b3ba75d45c0e6bbf715aff5ff40cbd24dcb22b473aad
Preview script
First 1,000 lines of the extracted script
�  �  �   @      ��������    �      Z       X   �  �  �             @   � �         � $                                    �  �  %      ��    & �  q           �  <         q         < 	   	   U         < 
       q         <         �&        <         ��        <         q         <         ��        <         ��        <         q         <         �         <         �3        <     �?  q         �  �  %      ��    &           �            X                                                               0                       3               	         
                             
                                                                                                                                                                                                       !         "         #         $         %         &         '         (         )         *         +         ,         -         .         /         0         1         2         3         4         5         6         7         8         9         :         ;         <         =         >         ?         @         A         B         C         D         E         F         G         H         I         J         K         L         M         N         O         P         Q         R         S   
     T   
     U   
     V   
     W   
     X   
   %      ��    &                        X                                                                                               	         
                             
                                                                                                                                                                                                       !         "         #         $         %         &         '         (         )         *         +         ,         -         .         /         0         1         2         3         4         5         6         7         8         9         :         ;         <         =         >         ?         @         A         B         C         D         E         F         G             H         I         J         K         L         M         N         O         P         Q         R         S   
     T   
     U   
     V   
     W   
     X   
   %      ��    &                        X                                                                                               	         
                             
                                                                                                                                                                                                       !         "         #         $         %         &         '         (         )         *         +         ,         -         .         /         0         1         2         3         4         5         6         7         8         9         :         ;         <         =         >         ?         @         A         B         C         D         E         F         G         H         I         J         K         L         M         N         O         P         Q         R         S   
     T   
     U   
     V   
     W   
     X   
   %      ��    &                        X                                                                                               	         
                             
                                                                                                                                                                                                       !         "         #         $         %         &         '         (         )         *         +         ,         -         .         /         0         1         2         3         4         5         6         7         8         9         :         ;         <         =         >         ?         @         A         B         C         D         E         F         G         H         I         J         K         L         M         N         O         P         Q         R         S   
 
... (truncated)