Office (OOXML) / .XLSX malware analysis — malicious · fd71a2fcc0b5dd0f

MALICIOUS

Office (OOXML) / .XLSX

123.0 KB Created: 2021-06-10 12:21:40 UTC Authoring application: Microsoft Excel 16.0300

MD5: 9e1ee4a42c381eabcf2cde38a1aae7c9 SHA-1: 015bb306d9e54001d433b3ac2e7212b864f54ae2 SHA-256: fd71a2fcc0b5dd0fb0dbff257839b67749f2cadf30e2d3dae7f0e941d93d24d3

120 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic T1059.001 PowerShell T1204.002 Malicious File

The sample is an Excel file containing VBA macros and an Excel 4.0 macro sheet. The VBA code uses CreateObject to instantiate a VBScript.RegExp object, which is then used to clean strings. The Excel 4.0 macro sheet contains references to 'cmd', indicating that it is likely intended to execute system commands. The combination of these elements suggests the file is designed to download and execute a secondary payload. No specific family could be identified.

Heuristics 3

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.
CreateObject call high OLE_VBA_CREATEOBJ

CreateObject call
VBA project inside OOXML medium OOXML_VBA

Document contains vbaProject.bin — VBA macros present

Extracted artifacts 3

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`macros.bas` `8640be0315e91d0a50bc49196517969d5fa0e0690c30285dfc6e423b717d4bb5`	vba-macro	oletools.olevba.extract_macros (decoded VBA source from OOXML)	651 bytes
`vbaProject_00.bin` `4e0f9431d478127398fb9073f650e67aade5f484a6de74f2f689d272761514e8`	vba-project	OOXML VBA project: xl/vbaProject.bin	12288 bytes
`xlm_sheet_00.bin` `3c2fe6c9d69950d339a7cc9c4b63729998d6e0bff49bbbd7af63a09d95d75de4`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	2164 bytes

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