Office (OOXML) / .XLSX malware analysis — malicious · cfd2995e6b3d5c01

MALICIOUS

Office (OOXML) / .XLSX

122.9 KB Created: 2021-03-29 19:54:41 UTC Authoring application: Microsoft Excel 16.0300

MD5: ab511590f6385bc8a2e5ff1a06292d07 SHA-1: ac023dc82980671057584851acabfa9f33fa4a96 SHA-256: cfd2995e6b3d5c0134ad4ab7a123afa0c8194d97e6acddc6e7158d8f86e17c01

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 the XLSX file. While the macro content is heavily truncated and obfuscated, the presence of this macro sheet strongly suggests an intent to execute arbitrary code. The likely purpose is to download and execute a secondary payload, a common technique for initial access or further system compromise.

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` `4ba2168210d43affdc2df39a4c02216ffe17c7afee4f75dbc3d4113362e4fe4d`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	96634 bytes

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