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

Static analysis result for SHA-256 98dc8f8eb20db5c2…

MALICIOUS

Office (OLE) / .XLSX

318.0 KB Created: 2020-05-20 11:46:01 Authoring application: Microsoft Excel
MD5: 9ee24fe2618f2b764c23684b0c3d1048 SHA-1: 759f18907013d39463948e70d30304407f7fd8fc SHA-256: 98dc8f8eb20db5c2a07d7bbc76de41faf678b991fcb7ff8da40dea596fe0de96
140 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic

The sample contains an Excel 4.0 macro sheet with an Auto_Open defined name, indicating it will execute macros automatically upon opening. The heuristics suggest an obfuscated execution chain involving RUN and FORMULA functions, which is a common technique for executing arbitrary commands or downloading further payloads. No specific family could be identified, and no external IOCs were extracted.

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.
  • Obfuscated XLM Auto_Open execution chain critical OLE_XLM_OBFUSCATED_AUTOEXEC_CHAIN
    Excel 4.0 macro sheet contains an Auto_Open / Auto_Close entry and an obfuscated formula execution chain. The macro builds strings through FORMULA(CHAR(...)), primes state with SET.VALUE / GET.CELL / GOTO, and transfers control through RUN(). This is a high-confidence XLM malware pattern.
  • 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
d2f05ddb67afaf26bd07da4afebd33d3b49d8683c1b3aace8289637847922b9f
xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 126252 bytes