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

Static analysis result for SHA-256 7d572dad3d0da6ea…

MALICIOUS

Office (OOXML) / .XLSX

24.5 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 14.0300
MD5: 541c1b091df1d5b4406509f3c966a643 SHA-1: 451245b0ab32f6439d37a9caf59234db5b1db303 SHA-256: 7d572dad3d0da6ead06f3dee1ad2fdcf6b8b1f1e26f2a8407813d6a097b69ef2
120 Risk Score

Malware Insights

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

The file contains Excel 4.0 macros, indicated by the OOXML_XLM_MACROSHEET heuristic. The OOXML_XLM_BINARY_WINAPI_STRINGS heuristic further reveals that these macros contain WinAPI calls such as URLDownloadToFileA, DownloadToFileA, ShellExecuteA, and CreateDirectoryA, along with references to URLMon and Kernel32. This strongly suggests the macro's purpose is to download and execute a second-stage payload from a remote location. The specific URLs and executable paths are not fully extractable due to truncation, but the presence of these WinAPI functions is a clear indicator of malicious intent.

Heuristics 2

  • 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.
  • 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.

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
99a6a52acb8f5c734f6d86faf89e0637a94ac99f953aa583d2658b47d2e1f9b9		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 194023 bytes

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