Office (OLE) / .XLSX malware analysis — malicious · 77d1768f3c182b54

MALICIOUS

Office (OLE) / .XLSX

36.5 KB Created: 2020-11-25 10:47:05 Authoring application: Microsoft Excel

MD5: af01b1e75a9b6be4ff345c0ae9825400 SHA-1: 8c4069157baa7d25fb8b1e023f911ccf7d1901f8 SHA-256: 77d1768f3c182b5447c51ce959087a3b988c0e3db32aede3cb7f7a183e02aa86

140 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic T1203 Exploitation for Client Execution

The file contains Excel 4.0 macros, specifically an Auto_Open function, which is a known method for executing malicious code within older Excel versions. The critical heuristics indicate the presence of dangerous formula APIs, suggesting the macro is designed to run arbitrary commands. The obfuscated document body content and the nature of XLM macros point towards a downloader or initial execution stage.

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` `90aaf92ce3bee78ab033efb319487263a5732112425f488ed82309d26e6ca8c3`	xlm-macro	oletools.olevba.extract_all_macros (XLM macro listing)	6782 bytes

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