Office (OOXML) / .XLSX malware analysis — malicious · a09c03f02092c61d

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 5e47b0181b32e78187961bdbeb80299f SHA-1: 64737216a596800ed83361f1fb01ee17099c7852 SHA-256: a09c03f02092c61db48bc44cbcb47ea22fe18f2f145080318b1bbe87a95e8407

120 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic for Applications

The sample is an XLSX file containing multiple Excel 4.0 macro sheets. This technique is commonly used to execute arbitrary code, often to download and run a second-stage payload. The macro content is heavily obfuscated and truncated, preventing a more detailed analysis of its specific actions or IOCs.

Heuristics 2

Excel 4.0 macro sheet (7 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 7

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`xlm_sheet_00.bin` `794319e8045b967a5f5158fadfe2510867fd96adc6f041d1c5e835243b0571f5`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet1.bin	2091 bytes
`xlm_sheet_01.bin` `8488125c759817c7eead6762c000300981461053df950751694de3aa1132db24`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	484 bytes
`xlm_sheet_02.bin` `1756459b1bb68c4d0598fd7bb70eb8bf6d3e38bfa332367839ae91070a9a402c`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet2.bin	484 bytes
`xlm_sheet_03.bin` `e758e60ae2698d0d92f0c76473963486b49f583e2e7982b50f9ef981162f9c20`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet3.bin	484 bytes
`xlm_sheet_04.bin` `b4d568af25776a79fe32c44981e0d6fa4ed0c74e7f65aa15cfcfbbe14f19e12c`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet4.bin	484 bytes
`xlm_sheet_05.bin` `fe03ff39a743f6804bd308389f2e1e2532a11a39f9fc263635dbc339db1da387`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet5.bin	484 bytes
`xlm_sheet_06.bin` `ba60892945dfe7b2413949de209c94148e3a4e3308d692894c141c441da9ca88`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet6.bin	484 bytes

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