Win.Malware.BazarLoader-9875319-0 — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 68ef8ffa46a0d0ea…

MALICIOUS

Office (OOXML) / .XLSX

182.3 KB Created: 2021-04-13 11:33:03 UTC Authoring application: Microsoft Excel 16.0300
MD5: 9d8889711256df5fba21cac45ff2be6e SHA-1: 72c600faaaf2168a46922b101589dff2c3579264 SHA-256: 68ef8ffa46a0d0ea1a981ad7bcfbaf1c7ad2680ddfac2a2d4b0822a23aaf4247
180 Risk Score

Malware Insights

Win.Malware.BazarLoader-9875319-0 · confidence 95%

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

The file contains critical heuristic firings indicating Excel 4.0 macros and a reassembled payload. The XLM macro sheet contains formulas that appear to construct a command to decode a payload using certutil. This is consistent with BazarLoader activity, which often uses macro-enabled documents to download and execute further stages.

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.
  • ClamAV: Win.Malware.BazarLoader-9875319-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Win.Malware.BazarLoader-9875319-0

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
f0fb1265d0f5e386869c8aba0a0f6ad9c15d5a60bd01f62713bd12a4d39cfd36		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 1861 bytes

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