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

Static analysis result for SHA-256 733c34e3e9598027…

MALICIOUS

Office (OLE) / .XLSX

36.0 KB Created: 2020-11-25 10:42:38 Authoring application: Microsoft Excel
MD5: 443fce1b84876b1f9840611dfdbdc0d7 SHA-1: 98327d3ce98a66882c13d188333c8257be2f5804 SHA-256: 733c34e3e95980275167593392463196addac912099bfce08eb63bc63005458f
140 Risk Score

Malware Insights

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

The file contains Excel 4.0 macros, specifically an Auto_Open function, which is a critical finding indicating potential malicious execution. The presence of dangerous formula APIs like RUN further supports this. The macro sheet is designed to execute arbitrary code upon opening, likely to download and run 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
bfa23cf6ef7f48a71fc6253acf207adb15bf9301046dc04548c9c3afa68004c6		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6580 bytes

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