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

Static analysis result for SHA-256 0aa9dce11120e9f9…

MALICIOUS

Office (OOXML) / .XLSX

69.8 KB Created: 2015-06-05 18:17:20 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2021-09-23
MD5: 062674fc07335bba28f2a5876152ef97 SHA-1: e65a9f199c52bf5cdc216d4a217729dc340cf421 SHA-256: 0aa9dce11120e9f924b01770bb8dd64120ba01cfc530ab03ba1715898ea9f96f
122 Risk Score

Malware Insights

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

The file contains Excel 4.0 macros which are designed to execute a PowerShell command. This command downloads and executes a second-stage payload from the URL http://35.163.204.167/oo. The use of XLM macros and the PowerShell downloader indicates a malicious intent to compromise the user's system.

Heuristics 3

  • 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.
  • 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.
  • 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://35.163.204.167/oo

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
68dbc9139ef76ff8d31cd71cb10f62e7c5b954c1bba3ec5917e1f6c775f56960		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 1291937 bytes

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