Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 ec298545cafeeba9…

MALICIOUS

Office (OOXML)

154.1 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2021-06-17
MD5: c4307e2ef61d11c3338f3e0144d4a83e SHA-1: 20000bff07f17d860be0c9b7915ca08daa19110c SHA-256: ec298545cafeeba94a63b03be8951d43f499a39b380724768caba1edd228b852
120 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1203 Exploitation for Client Execution

The sample is an Office Open XML document containing Excel 4.0 macros. The heuristics indicate that these macros are reassembled from split formulas and CHAR functions, suggesting an attempt to obfuscate a payload. The macros are likely intended to download and execute a second-stage payload from the embedded URL.

Heuristics 2

  • Excel 4.0 macro sheet (3 sheet(s)) critical 1 related finding 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.
  • 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.

Extracted artifacts 3

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.bin 5899 bytes
SHA-256: 3840a85fef597b4c1048e2293e9868c092cb71817ca6a48c70e385c15f054825
Preview script
First 1,000 lines of the extracted script
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... (truncated)
xlm_sheet_01.bin xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet2.bin 1178 bytes
SHA-256: e0ac2db23886cbd6e5c6d4571b4aed592c3b65d78fbc1c6914e8f5b1458839fe
Preview script
First 1,000 lines of the extracted script
�  �  �   @      ��������    �          &   4   �  %      ��                  & �  �             @   d           � $                                    �  �  %      ��    & �  �     ,     �  < /   /   m         < 0   4   �         �  �  %      ��    &           ,        &   2     &       %      ��    &   	       ,        &   2     &         2       %      ��    &   
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xlm_sheet_02.bin xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet3.bin 6260 bytes
SHA-256: e37bf8a7a6e81f7811bb1cee2f6fce3079bcd6a697aefbcf24f3cb728a30c452
Preview script
First 1,000 lines of the extracted script
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... (truncated)