Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 970c62ffb04d2e34…

MALICIOUS

Office (OOXML)

112.3 KB Created: 2021-02-03 15:28:44 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2021-06-04
MD5: 5257853803ac21d36e5a06a3d5fe75c0 SHA-1: 7e67707d031caf1393910edabb0939b1398f0401 SHA-256: 970c62ffb04d2e344f6011a0e0588977794eb79f2608aeb3cfdb8b4ab5aaff2d
184 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1203 Exploitation for Client Execution

The file contains disguised Excel 4.0 macros that are reassembled from split formulas. These macros are designed to download and execute a second-stage payload from the URL http://185.215.113.38/ao.exe, likely using 'wmic process call create' to launch the downloaded executable.

Heuristics 5

  • Excel 4.0 macro sheet (1 sheet(s)) critical 3 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.
  • Excel 4.0 macro sheet stored under disguised package path critical OOXML_XLM_DISGUISED_RELATIONSHIP
    OOXML package declares an xlMacrosheet relationship whose target is outside the canonical xl/macrosheets/ path. Excel follows the relationship type, while path-only scanners can miss the macro execution surface.
  • XLM payload reassembled from CHAR()/split formulas critical OOXML_XLM_REASSEMBLED_PAYLOAD
    An Excel 4.0 macro sheet builds its payload inside the formula token stream by concatenating per-character CHAR() calls and string fragments, so no WinAPI name, shell command, or URL is ever contiguous in the .bin for a literal-bytes scan to find. Reassembling the formulas recovered download/execute API names, LOLBin commands (regsvr32/rundll32/mshta/wmic/powershell), or a payload URL — the de-obfuscated download-and-run kill chain.
  • XLM payload URL string (1 URL) info OOXML_XLM_PAYLOAD_URL
    An Excel 4.0 (XLM) macro-sheet workbook with download/execute evidence carries a literal http(s) URL stored as a (often UTF-16) string in the shared-string table or a cell. This is the next-stage payload host referenced by the macro download chain (URLDownloadToFile/ShellExecute); surfaced as an IOC.
  • 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://185.215.113.38/ao.exe 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/do/sheet1.bin 960212 bytes
SHA-256: 246723ccd01ccdf96af98626b96cfc3172c037ff7dbdbb4c8e147446098830c4
Preview script
First 1,000 lines of the extracted script
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