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

Static analysis result for SHA-256 3138fb44058cfbe8…

MALICIOUS

Office (OOXML) / .XLSX

24.5 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 14.0300
MD5: b036120cf7a6a50e4929be440b110245 SHA-1: 5c2e4e1b3048ef6f6690b0bb22641c33c9ead1d5 SHA-256: 3138fb44058cfbe82a2abdb15e2b354359e39262dd421cd62ea4918732d89979
120 Risk Score

Malware Insights

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

The file is an Excel 4.0 macro sheet, identified by the OOXML_XLM_MACROSHEET heuristic. Critical heuristics indicate the presence of WinAPI strings related to downloading and executing files, specifically URLDownloadToFileA, DownloadToFileA, and ShellExecuteA. This suggests the macro's purpose is to download and execute a second-stage payload from a remote source. The file is therefore classified as a downloader.

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

Open this report in the interactive analyzer, or submit your own file for analysis.