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

Static analysis result for SHA-256 1f4daab1485f0a94…

MALICIOUS

Office (OOXML) / .XLSX

176.9 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000
MD5: 535dc017edc0cd66f53817cca2fb13d1 SHA-1: 05c69409fce4c60df2f83d0df38889186e6e3029 SHA-256: 1f4daab1485f0a94971fb687064bc479c91a4174631fa0e2f1e8f442c278a99b
60 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic

The sample is an Excel file containing Excel 4.0 macros. The macros appear to be obfuscated but reconstruct to a command that writes a file to C:\ProgramData\Microsoft\Windows\Start Menu\Programs\Start-up\GoogleUpdate.exe. This strongly suggests the intent is to download and execute a second-stage payload, likely for establishing persistence.

Heuristics 1

  • 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.

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
b1198c4b110984e47116489e92d06a96241fb177e5de835840ed68112ab49fc8		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 1837 bytes

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