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

Static analysis result for SHA-256 b91b0dd75b082180…

MALICIOUS

Office (OLE) / .XLSX

36.0 KB Created: 2020-11-27 11:38:21 Authoring application: Microsoft Excel First seen: 2023-03-30
MD5: 3f57a4bc544d99554cc22bf2830d382f SHA-1: e8b44bdc89d0d01711674e8d29fa2b1c0854d013 SHA-256: b91b0dd75b082180cbe8635b05a98410233831b5faae5168aee8f9299b5484fd
140 Risk Score

Malware Insights

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

The file contains Excel 4.0 macros, specifically an Auto_Open function, which is a known technique for executing malicious code upon opening the document. The critical heuristic firings indicate the presence of dangerous formula APIs like RUN, suggesting the macro is designed to execute arbitrary commands. No specific IOCs like URLs or hashes were extracted, but the technique itself is highly indicative of malicious intent.

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
c785801ac51cd0d1946c004cab4c973945b3d9a9a2da57aa18b78f89f0bf7da4
xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6694 bytes