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

Static analysis result for SHA-256 8757aad3002affb7…

MALICIOUS

Office (OOXML) / .XLSX

24.5 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 14.0300
MD5: 72d85fdad57d36760960f4bf102fd651 SHA-1: 8ff060f67060b68eb914ecc70e3ef4de758e0b26 SHA-256: 8757aad3002affb7a06a10fa6a13da8bcac73b3e87c1aeb065df1062f90f4cf3
120 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Service Execution: Service Execution T1204.002 Malicious File: Malicious File

The sample is an Excel file containing Excel 4.0 macros, as indicated by the OOXML_XLM_MACROSHEET heuristic. The OOXML_XLM_BINARY_WINAPI_STRINGS heuristic further reveals that these macros contain WinAPI calls related to downloading files and executing them, specifically mentioning URLDownloadToFileA, DownloadToFileA, and ShellExecuteA. This strongly suggests the macro's purpose is to download and execute a secondary payload from a remote location. The presence of .exe path indicators further supports this. Due to the obfuscated nature of the macro content, the exact URL and executable path could not be fully reconstructed.

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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