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

Static analysis result for SHA-256 aaf44246bca2cd7f…

MALICIOUS

Office (OLE) / .XLSX

36.0 KB Created: 2020-11-25 10:40:05 Authoring application: Microsoft Excel
MD5: 84225acddfe085eae01f367fa09314f6 SHA-1: 2b8f93a06d15862162b2c90475e61cd2475f9b9a SHA-256: aaf44246bca2cd7f7ecb0ff2fca977b5e472354a53180ed8637dfedb332b6b15
140 Risk Score

Malware Insights

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

The critical heuristics OLE_XLM_AUTOOPEN and OLE_XLM_DANGEROUS_FN indicate the presence of an Excel 4.0 macro sheet with an Auto_Open entry. The macro sheet contains a reference to the RUN function, which is a dangerous API that can be used to execute arbitrary commands. This suggests the file is designed to download and execute a second-stage payload upon opening.

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
81a310050156d58fa316cc2da89dea39b5ca39c9114f88dbd3ba7f564a571aa9		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6348 bytes

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