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

Static analysis result for SHA-256 da2bbbbea8edc8e3…

MALICIOUS

Office (OLE) / .XLSX

36.5 KB Created: 2020-11-27 11:42:40 Authoring application: Microsoft Excel
MD5: 0d209489dd7c69c5b329ed927d50fe46 SHA-1: 738bfad18e9aacb411d9e64cf252bdca305f7284 SHA-256: da2bbbbea8edc8e3da6e86315c0ca964be91e0b9ce510951fd8d622a2b63f46b
140 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1059.001 PowerShell

The sample is an Excel file containing Excel 4.0 macros, specifically an Auto_Open defined name. The critical heuristic firings indicate the presence of dangerous formula APIs within the XLM macro, including the RUN function, which is commonly used to execute arbitrary code. The macro sheet itself is named 'czkkrGwqG', and the Auto_Open entry points to a cell that likely contains the malicious code. The presence of the RUN function strongly suggests the macro is designed to download and execute a second-stage payload.

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
95e719fd96fd8516a73fcecade0a8115be9ca93db9a21ae6338becd069c01429
xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6938 bytes