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

Static analysis result for SHA-256 b1660b65514182bf…

MALICIOUS

Office (OOXML) / .XLSM

391.6 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 15.0300
MD5: 921ac551fe8d88c2185f39f0e777eabd SHA-1: 40702dc4f773cfa3fcf03c62ec810ba3f5e6b72d SHA-256: b1660b65514182bf97a767caa264b0500ef14692e69dae6ddca344591e7e016d
322 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1204.002 Malicious File T1105 Ingress Tool Transfer

The sample is an XLSM file containing Excel 4.0 macros, which are known to be used for malicious purposes. Critical heuristics indicate the use of dangerous functions like REGISTER, HALT, CALL, EXEC, and FORMULA, along with strings related to downloading files and creating directories. The macro sheet explicitly uses the functions 'DownloadToFileA', 'CreateDirectoryA', and 'RouteTheCall' to download a payload from 'http://gvbmkhvnyib.top/QtuFGobZaW/conhost.triumphloader'. This indicates the document's primary purpose is to act as a downloader for a second-stage payload.

Heuristics 7

  • 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 macro sheet stored under disguised package path critical OOXML_XLM_DISGUISED_RELATIONSHIP
    OOXML package declares an xlMacrosheet relationship whose target is outside the canonical xl/macrosheets/ path. Excel follows the relationship type, while path-only scanners can miss the macro execution surface.
  • 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: REGISTER, 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.
  • Binary XLM macro sheet with WinAPI/download strings critical OOXML_XLM_BINARY_WINAPI_STRINGS
    Excel 4.0 macro sheet is stored as BIFF12/XLSB binary data and contains Win32 download or process-execution API strings such as URLDownloadToFileA, ShellExecuteA, or CreateDirectoryA. These strings are high-signal in XLM macro sheets and catch payload-download macros that XML-formula scanners cannot parse.
  • NOP-equivalent sled detected medium SC_NOP_EQUIV_SLED
    Long run of 0x61 bytes
  • 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://gvbmkhvnyib.top/QtuFGobZaW/
    • http://gvbmkhvnyib.top/QtuFGobZaW/conhost.triumphloader
    • 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

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.xml
388f1568733b063db32c9dc1c8d771b2d8c4428a072e607da052bd47f8e62416		 xlm-macrosheet OOXML XLM macro sheet: xl/images/image1.png 1412338 bytes

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