Malicious Office (OOXML) / .XLSX — malware analysis report

Static analysis result for SHA-256 032d16df59c9a45e…

MALICIOUS

Office (OOXML) / .XLSX

155.0 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 16.0300
MD5: 67f1e54dd81e9c126975c8356d524a97 SHA-1: c3402eab0b72b805070d7b3e403da2db2a6c6344 SHA-256: 032d16df59c9a45e044e348443a18d830b9f895329587559f1316536733ae277
120 Risk Score

Malware Insights

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

The file is an Excel spreadsheet containing Excel 4.0 macros, as indicated by the OOXML_XLM_MACROSHEET heuristic. The OOXML_XLM_REASSEMBLED_PAYLOAD heuristic suggests that these macros are used to construct and execute a payload, likely by downloading it from a URL. The embedded XLM macros themselves are heavily obfuscated and truncated, preventing a more detailed analysis of their specific actions, but the presence of a URL fragment indicates a download attempt.

Heuristics 2

  • Excel 4.0 macro sheet (3 sheet(s)) critical 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
508ebb8d8a17285393862b61fecdeed5c080c23d0f0c6acb0ee14b69006c8270		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.bin 5827 bytes
xlm_sheet_01.bin
b34c069544e61839546fe6147d50d4d57faaab7f5999396424a57010ce22ac77		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet2.bin 1178 bytes
xlm_sheet_02.bin
b02fcdc5ad50c04571b013535f6c5281ce7e6fb4692238921aca64c643cfa115		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet3.bin 3882 bytes

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