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

Static analysis result for SHA-256 f0d7b006c4486da8…

MALICIOUS

Office (OOXML) / .XLSX

139.1 KB Created: 2021-09-20 10:27:09 UTC Authoring application: Microsoft Excel 12.0000
MD5: ad03732959490362bedc6b5b3da78db9 SHA-1: a60d818f0764e02b605f24ad3b157d435fde1547 SHA-256: f0d7b006c4486da873b3aa67512df23c8192ac590be01caf30a52138acc57172
120 Risk Score

Malware Insights

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

The sample is an Excel file containing Excel 4.0 macros, as indicated by the 'OOXML_XLM_MACROSHEET' heuristic. The ClamAV detection 'Xls.Downloader.Trojan-a0425f7f2000faff-a0425f7f2000faff-9950268-0' strongly suggests a downloader functionality. The macro sheet itself is heavily obfuscated, but the presence of downloader heuristics and the ClamAV signature point to the file's purpose of fetching and executing additional malicious content.

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: Xls.Downloader.Trojan-a0425f7f2000faff-a0425f7f2000faff-9950268-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.Trojan-a0425f7f2000faff-a0425f7f2000faff-9950268-0

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
1c9b1432d109c112457434c654172ebd884483c874b0fa6eef7edc0f8df20966		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 889 bytes

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