Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 e5773681382e61bb…

MALICIOUS

Office (OOXML)

142.9 KB Created: 2015-06-05 18:17:20 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2021-06-17
MD5: f5143d4ae2702dc0f18110da30385b97 SHA-1: e1c4cbd0cebafe38724ea59cc555ddd45c69cb6c SHA-256: e5773681382e61bbcd3acc96a844120a4f2808a89cb80e200d3f854828b233d3
120 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic

The file contains Excel 4.0 macro sheets, which are known to be used for malicious purposes. The heuristic 'OOXML_XLM_REASSEMBLED_PAYLOAD' indicates that the macro code was likely used to construct a URL, suggesting it's designed to download and execute a secondary payload. The specific URL 'https://' was reconstructed from split formulas within the macro sheets.

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 6043 bytes
SHA-256: d32efc890f8d678c4f7f726763ce14626df10566923007b6e4657be22c95a744
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 1210 bytes
SHA-256: 8c6ef244f1b5655417d57f29f2b866c60f538fb6fe24b0d818f3382f72b7314f
Preview script
First 1,000 lines of the extracted script
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xlm_sheet_02.bin xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet3.bin 5857 bytes
SHA-256: bef0998d7885927ea99b5d89ac0fb6c92b8b3ec6a42066e003a1824f1de3b019
Preview script
First 1,000 lines of the extracted script
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