Office (OOXML) / .XLSX malware analysis — malicious · 2d568e2e3fafc023

MALICIOUS

Office (OOXML) / .XLSX

101.2 KB Created: 2021-02-03 15:28:44 UTC Authoring application: Microsoft Excel 16.0300

MD5: 03a55bcad45de19f063a1c2d82f2c3d2 SHA-1: 99b7cb98089fb47faba3aac872ee6de1d71cc2a3 SHA-256: 2d568e2e3fafc0239205da89abe18eca67418da5baabe95cfaebff25a4858a7d

120 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The sample is an Excel file containing disguised Excel 4.0 macros. The heuristics indicate that these macros are stored under a disguised package path, suggesting an attempt to evade detection. The macros themselves are heavily truncated and obfuscated, preventing a detailed analysis of their specific actions. However, the presence of disguised Excel 4.0 macros strongly suggests a malicious intent, likely to download and execute a secondary payload.

Heuristics 2

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.
Excel 4.0 macro sheet stored under disguised package path critical OOXML_XLM_DISGUISED_RELATIONSHIP

OOXML package declares an xlMacrosheet relationship whose target is outside the canonical xl/macrosheets/ path. Excel follows the relationship type, while path-only scanners can miss the macro execution surface.

Extracted artifacts 1

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`xlm_sheet_00.bin` `438fad621ee310698a19b3ba75d45c0e6bbf715aff5ff40cbd24dcb22b473aad`	xlm-macrosheet	OOXML XLM macro sheet: xl/dpo/sheet1.bin	959417 bytes

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