Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 37c142525e58932c…

MALICIOUS

Office (OOXML)

142.9 KB Created: 2015-06-05 18:17:20 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2021-06-17
MD5: 3eefbe169215c8d8f4122e90d442660d SHA-1: 4e9baada22ccc58af4e047444dde534700d08ec4 SHA-256: 37c142525e58932cdba5e92c1e7af60839ef1fb12b737737e237bd9105ec2775
120 Risk Score

Malware Insights

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

The file contains Excel 4.0 macro sheets, which are known to be used for malicious purposes. The heuristics indicate that these macros are reassembling a payload from split formulas, likely to download and execute a second-stage payload from the embedded URL. The specific URL is truncated but begins with 'https://'.

Heuristics 2

  • Excel 4.0 macro sheet (3 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.
  • 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.

Extracted artifacts 3

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.bin 6043 bytes
SHA-256: 2d61c63d8cf5c6ed8559a213db7dd99bc66a29ab59598e2ce1f4fb7ff2155489
Preview script
First 1,000 lines of the extracted script
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... (truncated)
xlm_sheet_01.bin xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet2.bin 1210 bytes
SHA-256: b9a5f196a4a3785647a59db2287339a1140ff3a1ccaf05d6c5bc6d57c1001f13
Preview script
First 1,000 lines of the extracted script
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xlm_sheet_02.bin xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet3.bin 5857 bytes
SHA-256: 1d3fd4d50b61aca50b5d993d990c8ca33059615ddee074843b9f9e96527076e5
Preview script
First 1,000 lines of the extracted script
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