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

Static analysis result for SHA-256 3535766a6af60bb7…

MALICIOUS

Office (OOXML) / .XLSX

233.7 KB Created: 2021-03-05 04:08:28 UTC Authoring application: Microsoft Excel 16.0300
MD5: bbef9a9ddea88751fbd26054b57da8dc SHA-1: e027f2aabdefc87e7e558b4ee584a5a9af42fa3a SHA-256: 3535766a6af60bb7b3160db25c2249b0b52b019585a410be6c7d01fc723ad9d9
120 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic for Applications

The sample is an Excel 4.0 macro sheet, identified by the OOXML_XLM_MACROSHEET heuristic. ClamAV also detected it as a downloader trojan. While the script content is truncated, the presence of an Excel 4.0 macro sheet strongly suggests an attempt to execute code, likely to download and run a second-stage payload.

Heuristics 2

  • Excel 4.0 macro sheet (1 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.
  • ClamAV: Doc.Downloader.Trojan-bf70f023603538ee-bf70f023603538ee-9950269-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Doc.Downloader.Trojan-bf70f023603538ee-bf70f023603538ee-9950269-0

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
baa297bf7e389496ab4c6a90f6ca70b5fd988c9085ffb8cfa0034240b45e0eb5		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 11364 bytes

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