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

Static analysis result for SHA-256 583b5b61b363b7b2…

MALICIOUS

Office (OOXML) / .XLSX

24.5 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 14.0300
MD5: 4d09859f275ffde4067c003c68952b64 SHA-1: 600f1bdec839de4b461c37b30f225d4ef5936a85 SHA-256: 583b5b61b363b7b2852c2c0ae4a410273ab318b0cb4b268a2530d2a2155f0f3a
120 Risk Score

Malware Insights

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

The file contains critical heuristic firings indicating the presence of binary Excel 4.0 macros that utilize WinAPI functions for downloading and executing files. Specifically, the macros appear to use functions like URLDownloadToFileA and ShellExecuteA, suggesting an intent to download and run a second-stage payload. The presence of these functions and the nature of the heuristics strongly point towards a malicious downloader.

Heuristics 2

  • Excel 4.0 macro sheet (1 sheet(s)) critical 1 related finding 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
Preview script
First 1,000 lines of the extracted script
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... (truncated)