Malicious Office (OLE) / .XLSX — malware analysis report

Static analysis result for SHA-256 91c3426bc2246d50…

MALICIOUS

Office (OLE) / .XLSX

170.5 KB Created: 2014-08-26 06:49:00 Authoring application: Microsoft Excel
MD5: 70ecbdfccc2f05e9ff6f2da0016bd233 SHA-1: a99fc6e26167beb3c77ab5130c58231d8e0af279 SHA-256: 91c3426bc2246d50a255ef34fa8ead842d91a6d3dcbe3bcb97c8972821638deb
140 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1566.001 Spearphishing Attachment

The critical heuristics OLE_XLM_AUTOOPEN and OLE_XLM_DANGEROUS_FN indicate the presence of an Excel 4.0 macro sheet with an Auto_Open entry. This entry is configured to execute automatically when the workbook is opened. The macro sheet contains references to dangerous functions such as RUN, suggesting it is designed to download and execute a second-stage payload. The document body consists of seemingly random strings, which is common for obfuscated macro content.

Heuristics 3

  • Excel 4.0 Auto_Open defined name critical OLE_XLM_AUTOOPEN_DEFINEDNAME
    oletools recovered an Auto_Open / Auto_Close entry from an Excel 4.0 macro sheet. The raw BIFF name can be tokenized or partially opaque to byte-string checks, but the recovered macro listing confirms the workbook has an XLM auto-execution entry.
  • XLM Auto_Open with dangerous formula APIs critical OLE_XLM_DANGEROUS_FN
    Excel 4.0 macro sheet contains an Auto_Open / Auto_Close entry and dangerous XLM formula APIs that can invoke programs, write files, or transfer control without VBA.
  • Excel 4.0 (XLM) macro sheet present medium OLE_XLM_AUTOOPEN
    Workbook contains an Excel 4.0 macro sheet sub-stream — XLM is rarely seen in modern legitimate workbooks and was a major Office malware vector during 2020-2022.

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_macros.txt
5725c8e2e0df604395718efc7d09e28f0bafbb5a2db27c5118370e4dd4564225		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 79867 bytes

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