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

Static analysis result for SHA-256 6a61435c27762157…

MALICIOUS

Office (OOXML) / .XLSX

124.0 KB Created: 2021-03-22 09:18:04 UTC Authoring application: Microsoft Excel 16.0300
MD5: 67f0f93d82bcc598f5ea9186cf76ec54 SHA-1: 57bb1991de4ae0e7c51c6ccc1d0751ed082dc310 SHA-256: 6a61435c27762157a43c3043f953e82c3a912813d52bee0fe9aeb28ae3c36984
122 Risk Score

Malware Insights

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

The sample contains critical heuristic firings indicating the presence of Excel 4.0 macros. These macros are designed to reassemble a payload, specifically downloading a DLL from 'http://ballpro.xyz/campo/o/oC' and saving it to 'C:\ProgramData\flotsh\h4gf.dll'. The execution of this downloaded DLL is implied by the macro's 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://ballpro.xyz/campo/o/oC

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
a1503214fa651d8906b1bd77f8a3dcf330bc3912ebe8b5b7f27003000c47ac42		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 2612 bytes

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