Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 4658ade763bcdd56…

MALICIOUS

Office (OOXML)

357.7 KB Created: 2020-05-11 14:19:29 UTC Authoring application: Microsoft Excel 15.0300 First seen: 2020-12-25
MD5: 1588140404ad3787e431cb41272fd0eb SHA-1: 86170b492332c129319c03cce56cea7bee3cc8b2 SHA-256: 4658ade763bcdd56da300ea0599dd28eb7643c90d0829f32af57d5dfc44731d2
182 Risk Score

Malware Insights

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

The file contains Excel 4.0 macros, which are known to be used for malicious purposes. The macros contain strings indicative of downloading and executing a file, such as URLDownloadToFileA and ShellExecuteA. The reconstructed URL http://bluedict.com/ds/30.gif is likely used to fetch a second-stage payload.

Heuristics 4

  • Excel 4.0 macro sheet (1 sheet(s)) critical 2 related findings 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.
  • URL reconstructed from XLM cell array (1 URL) critical OOXML_XLM_CELL_ARRAY_URL
    Excel 4.0 macro sheet stages its payload URL across individual numeric cells (one ASCII charcode per cell), inside an embedded HTA that uses VBScript Chr()/&-concat obfuscation, or split across multi-char fragment cells a download formula concatenates by reference (=A1&A2&… / CONCATENATE(...)). The reconstructed URL is invisible to literal-bytes URL extraction because it is never contiguous in the workbook stream. URLs were recovered by walking the BIFF12 record stream of every worksheet and macrosheet part and decoding RK/inline-string/shared-string cells in row-major and column-major order plus FORMULA cell-reference concatenation in token order.
  • Embedded URL info EMBEDDED_URL
    One or more URLs were extracted from the document. The URL itself is not a detection — see the per-URL labels for which channel (macro, JS, link annotation, document body, ...) reached each URL.
    URL http://bluedict.com/ds/30.gif Referenced by macro

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 54253 bytes
SHA-256: 1a6ba314522f1d0b7b2b5e7679993b9cadfa17ca792c2dcc00c8174b343ec988
Preview script
First 1,000 lines of the extracted script
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... (truncated)

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