Office (OLE) / .XLSX malware analysis — malicious · 5521528541dc2b7c

MALICIOUS

Office (OLE) / .XLSX

36.0 KB Created: 2020-11-25 10:46:21 Authoring application: Microsoft Excel

MD5: 5f22dda486a4b5fc41749b40453abd4f SHA-1: ddeecd38b922a14f4d939462512d6893f046d59a SHA-256: 5521528541dc2b7cf4c5ea66d33f15594ddda5e603300b246174ba37f4fd4e2b

140 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic T1059.001 PowerShell T1059.003 Windows Command Shell

The file contains Excel 4.0 macros, specifically an Auto_Open defined name, which is a critical finding. The presence of dangerous formula APIs like RUN indicates that the macro is designed to execute commands. This is a common technique for downloading and executing a second-stage payload. The macro sheet itself contains obfuscated data, suggesting an attempt to hide its malicious intent.

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` `db67c466a24e3701ddc141157e30fabe344f4d3ebb05b7870bf954ef1ebdd286`	xlm-macro	oletools.olevba.extract_all_macros (XLM macro listing)	6387 bytes

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