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

Static analysis result for SHA-256 8cd0961f15cbe17f…

MALICIOUS

Office (OLE) / .XLSX

36.0 KB Created: 2020-11-27 11:40:41 Authoring application: Microsoft Excel
MD5: 3536fea63a54cf857ad817f7bfee8fac SHA-1: c43bc91298f187489dac8e014f6c5d9691575324 SHA-256: 8cd0961f15cbe17fd323e46ba02741054c7809a1537f87b928aae5de4bd8b4b4
140 Risk Score

Malware Insights

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

The file is an Excel spreadsheet containing Excel 4.0 (XLM) macros. Critical heuristics indicate the presence of an Auto_Open defined name, which is a common mechanism for automatic execution upon opening the document. The macro sheet contains a reference to the 'RUN' function, suggesting it is used to execute arbitrary commands. While the exact payload is not discernible from the provided evidence, the presence of an Auto_Open macro with a dangerous function points to a downloader or initial execution stage.

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
890c248dca50ae0d8caf44e080acba5e636ac3aec0ef96a42f8a4b4e0a244dee
xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6549 bytes