Qbot — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 6459ee50f5cc9a24…

MALICIOUS

Office (OOXML) / .XLSX

21.4 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 14.0300
MD5: 604f00c62664f6793120774d256ccd89 SHA-1: 6e41d133834b7e91aa7871acac91fca780de0662 SHA-256: 6459ee50f5cc9a24d58ea03afdfdaeea9370aef6d897c64cccf283ea96d4371c
240 Risk Score

Malware Insights

Qbot · confidence 95%

MITRE ATT&CK
T1059.005 Visual Basic T1203 Exploitation for Client Execution

The file contains critical heuristic firings indicating the presence of Excel 4.0 macros, which are reassembled from CHAR() and split formulas. These macros contain strings related to WinAPI functions such as URLDownloadToFileA, DownloadToFileA, and ShellExecuteA, suggesting the macro's purpose is to download and execute a secondary payload. The ClamAV detection name 'Xls.Dropper.QbotDocu12020-9818439-0' strongly suggests the Qbot family.

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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