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

Static analysis result for SHA-256 a71ef284e81915cf…

MALICIOUS

Office (OLE) / .XLSX

36.0 KB Created: 2020-11-25 10:46:37 Authoring application: Microsoft Excel
MD5: 5ef5e3db2cc21d4e2b7b9e8b17271480 SHA-1: 20f5a3f66675134a0041c95b65bc7d35d880d5b3 SHA-256: a71ef284e81915cf18b0e0293e6ab2c82a08b7744e58230ccaf3bb23732d02b2
140 Risk Score

Malware Insights

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

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. This macro sheet contains dangerous formula APIs, specifically the RUN function, which is used to execute arbitrary code. The macro sheet itself is named 'AvDoPWEvcOh', and the Auto_Open entry points to cell A151. 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
61ea1282590d5518b89a6987048eba076c31386c9756ba45706c2c7a4d0c0a0a		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6584 bytes

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