Office (OOXML) / .XLSX malware analysis — malicious · 7c880c51bcf1a2f5

MALICIOUS

Office (OOXML) / .XLSX

1.22 MB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2022-04-06

MD5: ad737e82f54c7f2f608474adef109f7d SHA-1: 307564014184227c80e32cd073701bda971cc7dd SHA-256: 7c880c51bcf1a2f5d8dfdce8b1bc9ff0cb1867f95bdfe911548ee4c6c3f18d56

140 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The sample is an Excel file containing multiple embedded Excel 4.0 macro sheets, flagged as critical heuristics. One of the macro sheets contains strings that appear to reference the 'C:\ProgramData' directory, suggesting a potential download or staging location for a second-stage payload. The presence of embedded OLE objects further supports the likelihood of malicious content.

Heuristics 3

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.
Embedded OLE object medium OOXML_OLE_OBJECT

Document contains an embedded OLE object

Extracted artifacts 6

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`ooxml_oleobject_00.bin` `d0ff51c01c1458568ad2f6fb078b16ec2f24b492e2d0cb89d63961ac8e529947`	ooxml-ole-object	OOXML embedded OLE part: xl/embeddings/oleObject1.bin	2263040 bytes
`ooxml_oleobject_00_ole10native_00.bin` `45f228642570d6f2de779122b0cdd1d811accdd0ae229de173fb524415b59b67`	ole-package	OOXML xl/embeddings/oleObject1.bin Ole10Native stream: Ole10Native	2243012 bytes
`emf_00.emf` `28a2af9cf0dcacb9693939904f250d2c6bc1017fd36bb28b549de84468d7f1ad`	ooxml-emf	OOXML EMF part: xl/media/image1.emf	4486440 bytes
`xlm_sheet_00.bin` `c7abb6dd98096c8188e7e0811ce0b33c7a22788ce247ea47da13a5111c118793`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet2.bin	896 bytes
`xlm_sheet_01.bin` `5d7fba7dd2d2b83908bd33b4d851ba4354e4f378c01d2d10786d52969a0aba93`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet3.bin	1206 bytes
`xlm_sheet_02.bin` `94e81ca813261a411918ce32ef537fb988cd8abac174ef9e6d2978d1bf292d9f`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet1.bin	608 bytes

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