Qbot — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 77de2853d8995628…

MALICIOUS

Office (OOXML) / .XLSX

21.4 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 14.0300
MD5: 13636f753fb049798e482082d944ca8e SHA-1: e9942be669ab0152f71c3103071d7aaa9a39c148 SHA-256: 77de2853d89956280984d7e43eb0b222ee9202f2973f0858ba15183a729358b3
240 Risk Score

Malware Insights

Qbot · confidence 95%

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

The file is an Excel 4.0 macro sheet that contains WinAPI strings related to downloading and executing files, such as URLDownloadToFileA and ShellExecuteA. The macros appear to be reassembled from CHAR() and split formulas, indicating an attempt to obfuscate the payload. The ClamAV detection name 'Xls.Dropper.QbotDocu12020-9818439-0' strongly suggests the Qbot family and a dropper functionality.

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.
  • Binary XLM macro sheet with WinAPI/download strings critical OOXML_XLM_BINARY_WINAPI_STRINGS
    Excel 4.0 macro sheet is stored as BIFF12/XLSB binary data and contains Win32 download or process-execution API strings such as URLDownloadToFileA, ShellExecuteA, or CreateDirectoryA. These strings are high-signal in XLM macro sheets and catch payload-download macros that XML-formula scanners cannot parse.
  • 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: Xls.Dropper.QbotDocu12020-9818439-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Dropper.QbotDocu12020-9818439-0

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
3fd5d57a928c8ba818db7c001502d9473d992f17b434009561c9d63b9b02fe10		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 22574 bytes

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