Office (OOXML) / .XLSX malware analysis — malicious · 7a13349625f35b88

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 33dd89f685dd84135f870193bb85574b SHA-1: 227f339a9157d254a5b5a2f2770dbb989b0b6fc1 SHA-256: 7a13349625f35b885ce8a48cde247e1aeaad7cc54df452890f43c524556470f4

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The critical heuristic firing indicates the presence of Excel 4.0 macros within an XLSX file. Analysis of the embedded XLM macro sheet reveals commands that appear to construct and execute a path to a program, likely a downloader. The macro attempts to write to C:\ProgramData\a.exe, suggesting it's designed to download and execute a second-stage payload.

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` `734c8ab75ff2b3bb6905f7c3a10e768d7e89c57afdf610b839198b6dedc77713`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	7213 bytes

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