Office (OOXML) / .XLSX malware analysis — malicious · da954e82c9fe0cbc

MALICIOUS

Office (OOXML) / .XLSX

1.16 MB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2022-03-29

MD5: a24bc9f2fc5095861df112e32f721465 SHA-1: 5117fb60be91044b20ca9f6a0d887cc749dd9970 SHA-256: da954e82c9fe0cbc713547393b50f5b449396ce8059a6a049ee51c7440427c61

120 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The sample is an XLSX file containing multiple Excel 4.0 macro sheets. These macros are known to be used for executing arbitrary commands, often to download and run further malicious content. The obfuscated nature of the macro content prevents a more detailed analysis of the specific payload or execution chain.

Heuristics 2

Excel 4.0 macro sheet (3 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.
XLSB international XLM macro sheet hidden in .xlsx critical OOXML_XLSB_INTL_MACROSHEET_IN_XLSX

OOXML package is named .xlsx but contains XLSB workbook parts and an international Excel 4.0 macro sheet. This hides XLM macro execution from scanners that trust the extension or only inspect XML worksheet parts. The technique is macro execution, not a document-parser CVE.

Extracted artifacts 4

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`emf_00.emf` `a12daa770fc1848e39c880d90376e8e5b6814576e9bdbfaa076685fd9b9b2ba3`	ooxml-emf	OOXML EMF part: xl/media/image1.emf	6145428 bytes
`xlm_sheet_00.bin` `94dcae400bad291e7734b3303be72f72bc74b4ef3f7737fe960644bb383a7a69`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	484 bytes
`xlm_sheet_01.bin` `6b69a539d2d44586cd29d86a91c29f1e2ba8aa4a323b5a4a9f7f0d23cd002d42`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet2.bin	484 bytes
`xlm_sheet_02.bin` `46ff111a4683eea3ae97021320d38aa4eb315350d26452c986cde8fd19a80a92`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet1.bin	2165 bytes

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