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

Static analysis result for SHA-256 e3d8d4908bf4f829…

MALICIOUS

Office (OLE) / .XLSX

36.0 KB Created: 2020-11-25 10:40:02 Authoring application: Microsoft Excel
MD5: 405751df1a835b6a9effa797604bcccb SHA-1: ee371591babf57d0bb331b1cd40e6d1aa1301cbb SHA-256: e3d8d4908bf4f8296cdddf62a458de511536184b89c72069e0a4c4f7c56eda47
140 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1059.001 PowerShell T1059.003 Windows Command Shell

The sample contains Excel 4.0 (XLM) macro sheets with an Auto_Open defined name, indicating automatic execution upon opening. Critical heuristics fired for the presence of XLM macros and the use of dangerous formula APIs, specifically the RUN function. This suggests the macro is designed to execute arbitrary commands, likely for downloading and executing a second-stage payload. No specific IOCs were extracted, but the technique 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
c0277a6c8612910d37407c2e769b528ead523f4dadbea51ec024ef149c8af84e
xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6645 bytes