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

Static analysis result for SHA-256 74695a18d8ab2d6e…

MALICIOUS

Office (OLE) / .XLSX

35.5 KB Created: 2020-11-25 10:39:41 Authoring application: Microsoft Excel
MD5: 67a9f0b679ba1de6ea6bdab93301338d SHA-1: f71cab22e174cb5d9882003100fe5ed79340e961 SHA-256: 74695a18d8ab2d6e079f117d0b9f2566112e2da2585ddca7539b3c575c74f020
140 Risk Score

Malware Insights

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

The critical heuristics indicate the presence of Excel 4.0 macros with an Auto_Open defined name and the use of dangerous formula APIs, specifically the RUN function. This strongly suggests the macro is designed to execute arbitrary code upon opening the document. The presence of the Auto_Open entry is the primary IOC, pointing to the execution mechanism.

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
214e2155230ce87ba595a7240068e97e1acb77d51c21528aad8a4aeb068a33d2		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6442 bytes

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