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

Static analysis result for SHA-256 630167d6ab29c3da…

MALICIOUS

Office (OOXML) / .XLSX

233.7 KB Created: 2021-03-05 04:08:28 UTC Authoring application: Microsoft Excel 16.0300
MD5: e8f6e9dc434ee5c75c5432e5f11eb3d4 SHA-1: b62c4206f49b4022b700cc299d61ec3463009805 SHA-256: 630167d6ab29c3da55ef2a691557608f0a6d9173d668af7a48307c54c7e0ec49
182 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1204.002 Malicious File

The file contains Excel 4.0 macros that are designed to download a DLL payload from the URL http://195.123.222.194/campo/h/hC and save it to C:\ProgramData\flotsh\h4gf.dll. This indicates a downloader or droppper functionality, likely leading to further malicious activity. The ClamAV detection further supports its malicious nature.

Heuristics 4

  • 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.
  • ClamAV: Doc.Downloader.Trojan-bf70f023603538ee-bf70f023603538ee-9950269-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Doc.Downloader.Trojan-bf70f023603538ee-bf70f023603538ee-9950269-0
  • 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://195.123.222.194/campo/h/hC

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
6ad77f7a9273b686318172f36887be18acc75eb2598f70f0fac9b759413351e0		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 11364 bytes

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