Office (OLE) / .XLSX malware analysis — malicious · 45c79dc9016a9bf1

MALICIOUS

Office (OLE) / .XLSX

36.5 KB Created: 2020-11-27 11:30:22 Authoring application: Microsoft Excel

MD5: be3b199ab9f89f9f983979d2ca322668 SHA-1: 3736f7a6c912c15056b3bfce780df4e945967a19 SHA-256: 45c79dc9016a9bf11909181fdeec295d442bedf368425d9c1dae8fb4cc57cfa0

140 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic T1059.001 PowerShell T1204.002 Malicious File

The sample is an Excel file containing Excel 4.0 macros, specifically an Auto_Open defined name. Heuristics indicate the use of dangerous formula APIs within the XLM macro, such as the RUN function, which is commonly used to execute arbitrary commands. This suggests the macro is designed to download and execute a second-stage payload. No specific URLs or hashes were extracted, limiting further IOC identification.

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` `f48c73b5e75952784439047fdc9ffbe77c8f8f00e2472c05bb0045dfc516cd14`	xlm-macro	oletools.olevba.extract_all_macros (XLM macro listing)	6637 bytes

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