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

Static analysis result for SHA-256 76cda7f71e1d2ef3…

MALICIOUS

Office (OOXML) / .XLSM

593.3 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300
MD5: dff02f2f06a27f87461540d1a89d1b43 SHA-1: 505986cdccc25f6d62309b7376168383c08b61bf SHA-256: 76cda7f71e1d2ef34baea9bd1424bb9dfd7cba9d8890abcc04d62640583fa439
248 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic for Applications T1204.002 Malicious File

The file is an XLSM document containing Excel 4.0 macros. Critical heuristics indicate the use of dangerous XLM formula APIs like EXEC, which are commonly used to download and execute payloads. The presence of hidden sheets further suggests an attempt to conceal malicious activity. The ClamAV detection confirms its malicious nature as a downloader. The embedded URLs are benign, but the core functionality relies on the XLM macros to initiate the attack chain.

Heuristics 6

  • 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: EXEC, HALT 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.
  • ClamAV: Xls.Downloader.GreenEnable052-9863734-1 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.GreenEnable052-9863734-1
  • Hidden worksheet (hidden) low OOXML_HIDDEN_SHEET
    Excel workbook contains 2 hidden sheet(s) — hidden sheets are commonly used to conceal macro code, staging data, or intermediate payload construction
  • 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://ns.adobe.com/xap/1.0/
    • http://www.w3.org/1999/02/22-rdf-syntax-ns#
    • 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
ff1734ec2098b716792e5cfacd8b495899f0f9820516f5553a76fc028d540863		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 2472 bytes

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