Office (OOXML) / .XLSX malware analysis — malicious · e9ac6c6ba533f52d

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 547a4b9ebe0452fc106483b134a9c044 SHA-1: a1ce1cace39ca1b0c46eac10ddfc457fc1766ac8 SHA-256: e9ac6c6ba533f52db849035ac04b3b3dcbd769cc2d67470bdb30c40f962b8ffc

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The file is an Excel 4.0 macro sheet, indicated by the OOXML_XLM_MACROSHEET heuristic. The macro sheet contains obfuscated strings that reconstruct to a file path 'C:\ProgramData\excel.rtf'. This suggests the macro's purpose is to write or execute content from this path, likely as part of a malicious payload delivery chain. The exact execution flow is unclear due to truncation, but the presence of Excel 4.0 macros points to a common initial access vector.

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` `e2da8a34e13ef3d2e455a32407d936b38d748279b35b337c4d7db43b858a716d`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	167244 bytes

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