Office (OLE) / .XLSX malware analysis — malicious · 91777d1c3a88f8c3

MALICIOUS

Office (OLE) / .XLSX

70.5 KB Created: 2015-06-05 18:19:34 Authoring application: Microsoft Excel First seen: 2022-05-27

MD5: cda1ddb3f94c25b4b787fd4bbb9641e8 SHA-1: dd03a53ad84d258af9112eeb52b17a91d5a5a74f SHA-256: 91777d1c3a88f8c324d1dc16007113aa070c718f234e9dec05c5c2930fd39edf

140 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic for Applications T1204.002 Malicious File

The file contains Excel 4.0 macros, specifically an Auto_Open function, which is a critical finding. This function is designed to execute dangerous formula APIs, including RUN, indicating it's intended to launch external code. The macro likely downloads and executes a second-stage payload from one of the provided URLs. The presence of multiple suspicious URLs further supports this conclusion.

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` `699e21f010c7c5f5713063f52e691ec519f766e81393f8793f7a585cd43d5349`	xlm-macro	oletools.olevba.extract_all_macros (XLM macro listing)	7635 bytes

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