Office (OLE) / .XLSX malware analysis — malicious · 640c8d3cec3d445b

MALICIOUS

Office (OLE) / .XLSX

35.5 KB Created: 2020-11-25 10:45:04 Authoring application: Microsoft Excel

MD5: 520baf36a5514a483ad63cef4b358cf6 SHA-1: e0ab3d709210172d239e0e6d08ad43e4c0b26baf SHA-256: 640c8d3cec3d445bcaced29ee4426c5de7a748f8442b951c0a6f6cacb9e227c3

140 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic T1203 Exploitation for Client Execution

The critical heuristics indicate the presence of Excel 4.0 macros with an Auto_Open defined name and dangerous formula APIs, specifically the RUN function. This strongly suggests the macro is designed to execute arbitrary code upon opening the spreadsheet. The presence of a macro sheet named 'JSFBMGPL' further supports this. The macro is likely a downloader for a second-stage payload, though no specific URLs or hashes 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.
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.

Filename	Kind	Source	Size
`xlm_macros.txt` `42012c88418fc762f1afca4d998490db8ee0bb83398a4a5e30f02437aeaee9d9`	xlm-macro	oletools.olevba.extract_all_macros (XLM macro listing)	6486 bytes

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