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

Static analysis result for SHA-256 39099ffe8f712a20…

MALICIOUS

Office (OLE) / .XLSX

37.0 KB Created: 2020-11-27 11:38:37 Authoring application: Microsoft Excel
MD5: e47d13f2580fb2f5a7f2ee2c6a47c176 SHA-1: 3291d6ab6d4bec15802250c5fb09cf87cd66118a SHA-256: 39099ffe8f712a20039f63cca72bbf95cf41f5c91950f29bf4b61de394da98d2
140 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic

The file contains Excel 4.0 macros, specifically an Auto_Open function, which is a known method for executing malicious code upon opening the workbook. The critical heuristic firings confirm the presence of a dangerous formula API within the Auto_Open macro, indicating an intent to run arbitrary commands. No specific IOCs like URLs or hashes were extracted, but the technique itself 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
d499bafc0dbdb171a86e23100db3c855a6810f96aadbd51949416bb6ee6fb6b3		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6863 bytes

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