Malicious Office (OOXML) / .XLSM — malware analysis report

Static analysis result for SHA-256 02780494d2cf9889…

MALICIOUS

Office (OOXML) / .XLSM

25.0 KB Created: 2021-03-11 11:07:15 UTC Authoring application: Microsoft Excel 16.0300
MD5: b337c349b27bf4f1c13312c97ee9a516 SHA-1: 989b07482c375a234a2df6cbfcd5a2baef408931 SHA-256: 02780494d2cf988930f92a35e01dd624dcb7f6d185689813d4862799a7faf2e1
182 Risk Score

Malware Insights

MITRE ATT&CK
T1566.001 Spearphishing Attachment T1059.005 Visual Basic T1203 Exploitation for Client Execution

The sample is an XLSM file containing Excel 4.0 macros, indicated by the 'OOXML_XLM_MACROSHEET' and 'OOXML_XLM_AUTOOPEN_DEFINEDNAME' heuristics. The 'OOXML_XLM_DANGEROUS_FN' heuristic confirms the use of dangerous XLM formula APIs like FORMULA, which can be used to download and execute payloads. The document body prompts the user to 'Enable Editing' and 'Enable Content', a common lure for macro-enabled malicious documents. The specific macro code is truncated, but the presence of these dangerous functions strongly suggests a payload download and execution attempt.

Heuristics 4

  • 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.
  • Excel 4.0 Auto_Open defined name critical OOXML_XLM_AUTOOPEN_DEFINEDNAME
    Workbook defines _xlnm.Auto_Open or _xlnm.Auto_Close while containing an XLM macro sheet. This is the OOXML/XLSB auto-execution shape for Excel 4.0 macros.
  • Dangerous XLM formula APIs: FORMULA critical OOXML_XLM_DANGEROUS_FN
    Excel 4.0 macro sheet uses formula APIs that call directly into Win32 (=CALL/=EXEC/=REGISTER/=FORMULA). These are the primitives used to download payloads, write files, and start processes from an XLM macro without invoking VBA.
  • Embedded URL info EMBEDDED_URL
    One or more URLs were extracted from the document. The URL itself is not a detection — see the per-URL labels for which channel (macro, JS, link annotation, document body, ...) reached each URL.
    URL http://schemas.openxmlformats.org/spreadsheetml/2006/main
    • http://schemas.microsoft.com/office/excel/2006/main
    • http://schemas.openxmlformats.org/officeDocument/2006/relationships
    • http://schemas.openxmlformats.org/markup-compatibility/2006
    • http://schemas.microsoft.com/office/spreadsheetml/2009/9/ac
    • http://schemas.microsoft.com/office/spreadsheetml/2014/revision
    • http://schemas.microsoft.com/office/spreadsheetml/2015/revision2
    • http://schemas.microsoft.com/office/spreadsheetml/2016/revision3
    • http://schemas.microsoft.com/office/spreadsheetml/2016/revision6

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.xml
1d10747fc38eca541b6ea8d605d8a323c79ca4199cd410065191c676df62f0e9		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 20579 bytes

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