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

Static analysis result for SHA-256 3b121ece72676422…

MALICIOUS

Office (OOXML) / .XLSX

1.05 MB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2022-05-11
MD5: 734c11aa8847bc6169fd56dacb482591 SHA-1: d6967236d7775d8291777e125372bf0e58b0e97e SHA-256: 3b121ece72676422e17261e8e7358c7451298bb59bd45cccde2a9236c7fb4365
120 Risk Score

Malware Insights

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

The sample contains Excel 4.0 macros, identified by the OOXML_XLM_MACROSHEET heuristic. These macros attempt to create directories and download files using WinAPI calls like CreateDirectoryA, as indicated by the OOXML_XLM_BINARY_WINAPI_STRINGS heuristic. The reconstructed URLs and filenames suggest a download and execution chain, likely involving Regsvr32. The specific URLs and paths are: 85.239.54.156, 85.82.127.96, 185.106.120.77, C:\Frast, C:\Frast\Drest, C:\Frast\Drest\Astop.OOCCXX, and C:\Frast\Drest\Astop1.OOCCXX.

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 2

Files carved from inside the sample during analysis.

FilenameKindSourceSize
emf_00.emf
9e7c55c3426bae6c8002b3f78793ea39557b0be5b80a04ea4bbe028eae8b0ba3		 ooxml-emf OOXML EMF part: xl/media/image2.emf 1048628 bytes
xlm_sheet_00.bin
f04f8e1559784e10132d173a06df811c938149a139616950cdafd54b648c3842		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 2789 bytes

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