Office (OOXML) / .XLSX malware analysis — malicious · 1c356f9da7290f89

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 69e645b731fe0d12d4d470b44091075d SHA-1: 2fe622d805269567b56ab492eb0513840b9f547c SHA-256: 1c356f9da7290f89ee0e8332cb2892c6f1cecc744cf2e31591de1da01b01d498

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The critical heuristic firing indicates the presence of an Excel 4.0 macro sheet. Analysis of the macro content reveals it uses 'wmic process call create' to execute a file named 'excel.rtf' located in the 'C:\ProgramData\' directory. This suggests the macro's purpose is to download and execute a second-stage payload from that location.

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` `807ca831fbc900bd425f49e7dea4fc2d7680ab70de23e727cabe20a5c63825b2`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	159794 bytes

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