Qbot — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 6306a8279d6dafe6…

MALICIOUS

Office (OOXML) / .XLSX

21.4 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 14.0300
MD5: e93cf1d60efd4e387b705c8a6f9b1d15 SHA-1: 043100cba28ba3631a7abd4d4b73dd911bb46deb SHA-256: 6306a8279d6dafe63592c7cd2a074a7b168cdafdc3ed95b09bb44b438bff4d2e
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 contains critical heuristic firings indicating the presence of Excel 4.0 macros. These macros are designed to reassemble and execute a payload, utilizing WinAPI functions like URLDownloadToFileA to fetch a second-stage executable. The ClamAV signature further confirms its classification as a Qbot dropper.

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
852f8a9074f0a60640376457fa2c0441f9a473e65357dd598131fc2c795c0e21		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 22574 bytes

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