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

Static analysis result for SHA-256 5c097be39146bcc3…

MALICIOUS

Office (OOXML) / .XLSX

78.8 KB Created: 2021-03-16 13:14:06 UTC Authoring application: Microsoft Excel 16.0300
MD5: e41235a49dc61eed4e646cbb1e753269 SHA-1: f112798b52fa845fb04531dfd49d825cfbcfcb30 SHA-256: 5c097be39146bcc3f26cba610fb420ac6ff5b3d9ad8f145e801eeba6facea50c
122 Risk Score

Malware Insights

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

The sample contains Excel 4.0 macros that are designed to download a DLL payload from the URL http://sported.xyz/campo/g/g and save it to C:\ProgramData\flotsh\h4gf.dll. The macros also attempt to execute the downloaded DLL. This indicates a downloader or droppper functionality.

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://sported.xyz/campo/g/gC

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
960eead5d186f61aa44366e101e52155471e4706d2a28a55eb84498e5a62e3d7		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 2544 bytes

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