Qbot — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 18a1d3f49eea4ed2…

MALICIOUS

Office (OOXML) / .XLSX

23.6 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 14.0300
MD5: bbd1d1d921f5dbc47ea936a68a38308c SHA-1: 2be08a8fab766b97e79eecc3c0b2d6a4b3824dd8 SHA-256: 18a1d3f49eea4ed203809733d45fe4331a366dc1e692554def7aa4f047ab73d7
240 Risk Score

Malware Insights

Qbot · confidence 95%

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

The sample is an Excel file containing Excel 4.0 macros, identified by multiple critical heuristics. These macros utilize WinAPI functions like URLDownloadToFileA and ShellExecuteA to download and execute a second-stage payload, as indicated by the 'Xls.Dropper.QbotDocu12020-9818439-0' ClamAV detection name. The macro logic appears to be reassembled from CHAR() and split formulas, a common technique for obfuscation.

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
581964282792c79e613320e827a7b43dd0b0bd59b511ea08bac1e7be04d2efb4		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 27387 bytes

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