Office (OOXML) / .XLSX malware analysis — malicious · e9d1338224a412ac

MALICIOUS

Office (OOXML) / .XLSX

123.8 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300

MD5: ca411789676bc7da84ff9aee1e13f17c SHA-1: b3ff989c83c76cd0654e8d27f6c5e6c081c1e054 SHA-256: e9d1338224a412acbf0924f81ded63ef9c52d4cc6a1b8dd2094ee39a6a7984bc

180 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The sample is identified as malicious by ClamAV with the signature Xls.Downloader.GreenOffice01223-9937701-0. Static analysis revealed the presence of multiple Excel 4.0 macro sheets, indicating a macro-based execution flow. These macros are likely responsible for downloading and executing a secondary payload, a common technique for malware delivery.

Heuristics 3

Excel 4.0 macro sheet (8 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.
ClamAV: Xls.Downloader.GreenOffice01223-9937701-0 critical CLAMAV_DETECTION

ClamAV detected this file as malware: Xls.Downloader.GreenOffice01223-9937701-0

Extracted artifacts 8

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`xlm_sheet_00.bin` `601e373374d41fdd36dd907ce4e8dc0dc0e62d3cf33bbc6cf8c27500b3b2183f`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet3.bin	428 bytes
`xlm_sheet_01.bin` `789c86435dced37b9809e0d14afad4ae4bec773ba94488e1a402ea2607098acf`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet7.bin	428 bytes
`xlm_sheet_02.bin` `75546976956b41175dda83afb5dd2f36972a4c8ee8479a35e3c993561a13e40f`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet1.bin	2080 bytes
`xlm_sheet_03.bin` `fa2cdb3f36be3e136711bb0f17877a81a3075c3aa1f9577263203e20e17563b6`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet4.bin	428 bytes
`xlm_sheet_04.bin` `3a4f7457134bada0037c22b38f7a80bf2ab71f1bea3b2529ecec0ec1f8c4a567`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	428 bytes
`xlm_sheet_05.bin` `9503a7e1b54a411a5384744a0235d0aa88ebdfcc1d955d8bb046efd02166e80e`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet6.bin	428 bytes
`xlm_sheet_06.bin` `d467663aa96d2dc4437dcdc2fe587f90ebd44488e841fa9404c0820dcc29eda3`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet2.bin	428 bytes
`xlm_sheet_07.bin` `81cd2db898416c2ec8e340d66f358552cf450627a515990768e25ebfeee99983`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet5.bin	428 bytes

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