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

Static analysis result for SHA-256 b7edef6dfcbf61c6…

MALICIOUS

Office (OOXML) / .XLSX

24.5 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 14.0300
MD5: 1cc885934121ed33b90c32e6be3baed6 SHA-1: dba26bce6278892260ee86b3b3412175ac02f9de SHA-256: b7edef6dfcbf61c694dd32b09889aa08f1e547babf51e29d875f6bdd7ac87f24
120 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic for Applications T1105 Ingress Tool Transfer

The sample contains critical heuristic firings indicating the presence of Excel 4.0 macros with WinAPI and download strings. These strings, including URLDownloadToFileA, DownloadToFileA, ShellExecuteA, CreateDirectoryA, URLMon, and Kernel32, strongly suggest the macro's intent is to download and execute a second-stage payload from a remote source. The file is an Excel 4.0 macro sheet, which is a common delivery mechanism for initial compromise.

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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