Office (OOXML) / .XLSX malware analysis — malicious · c14b974e42e730a5

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: a9f09441e8b6fea4b043de2b3ea3009a SHA-1: d6047abe8ba12fffa2d984510c391a2ce6e450ff SHA-256: c14b974e42e730a55e610964fb0bce6a8429bd31c6b71d35c82caf4015a3a921

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic for Applications

The sample contains an Excel 4.0 macro sheet, which is a known technique for delivering malicious payloads. The macro appears to be constructing paths for a second-stage payload, likely a VBScript or executable, to be downloaded and executed from the C:\ProgramData\aam\ directory. The specific filenames constructed suggest a downloader or dropper functionality.

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` `8e47b4a9e0770f4c696904ce96c8182b9446b28682f9fa3227f2277adfbfa910`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	3705 bytes

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