Office (OOXML) / .XLSX malware analysis — malicious · 4d0d72652f327435

MALICIOUS

Office (OOXML) / .XLSX

95.5 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000

MD5: a84a7aa838464b13983112c076a0361e SHA-1: 89d857033b0d793de486e530f6cd2a4c271ee13a SHA-256: 4d0d72652f327435a620b13744630f4c1bfbdaaabf983a2fae9bd4602ac1d0ce

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The sample is an Excel file containing Excel 4.0 macros, indicated by the OOXML_XLM_MACROSHEET heuristic. The macro sheet appears to contain obfuscated commands, including a path that reconstructs to 'C:\ProgramData\excel.rtf'. This suggests the macro's purpose is to execute code from this location, likely a downloader for a second-stage payload. The family is unknown due to the lack of specific indicators.

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.

Filename	Kind	Source	Size
`xlm_sheet_00.bin` `a310608482febed1bdf43066d619100346cae5639e9974e909635e2d8e94813b`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	131890 bytes

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