Office (OLE) / .XLSX malware analysis — malicious · a8c12aa6ab752880

MALICIOUS

Office (OLE) / .XLSX

70.5 KB Created: 2015-06-05 18:19:34 Authoring application: Microsoft Excel First seen: 2022-05-26

MD5: f9bafa1bb284cb801d84995b004d7c47 SHA-1: b65be55625d084cf803def7cf57e11e0545597e8 SHA-256: a8c12aa6ab752880d44f9707bf2af6c2ec287b870a99308c4393c3b0b9c20258

140 Risk Score

Malware Insights

MITRE ATT&CK

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

The sample contains Excel 4.0 macros, specifically an Auto_Open function, which is a critical finding. This macro is designed to execute dangerous formula APIs, including RUN. The macro sheet contains multiple URLs that are likely used to download and execute a second-stage payload. The presence of the Auto_Open function and the execution of external resources strongly indicate a malicious intent for payload delivery.

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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