Office (OOXML) / .XLSX malware analysis — malicious · c76b79576cd159ad

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: a20fc00964b9bd95e21d7b0eb3e69c1e SHA-1: 67099a9f9592ccd20637d748be7d2a68181b0941 SHA-256: c76b79576cd159ad4a3afb1900d0da04be8f812a771b913aa3113b5102c1bd06

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The sample is an Excel file containing embedded Excel 4.0 macros, indicated by the OOXML_XLM_MACROSHEET heuristic. The macros appear to be attempting to write a file to disk at 'C:\ProgramData\excel.rtf', likely as a precursor to executing a malicious payload. The exact execution mechanism is unclear due to truncation, but the presence of macros and the file path strongly suggest a malicious intent.

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` `f2c5c01e73cd9959d6c358cdc165b48935764b59ffb3e264267e7115cc292024`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	113587 bytes

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