Office (OLE) / .XLSX malware analysis — malicious · 527326a708bd2e15

MALICIOUS

Office (OLE) / .XLSX

36.0 KB Created: 2020-11-25 10:38:05 Authoring application: Microsoft Excel

MD5: 16b1c6ac0240a60343784bfeab02d675 SHA-1: af43e9c4713154ca5934c183181f1144ce014972 SHA-256: 527326a708bd2e154d3d67a823ef2ed8389b63cce55d0739b5cebecab068202a

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 (XLM) macro sheets, specifically triggering an Auto_Open event. The critical heuristic OLE_XLM_DANGEROUS_FN indicates the use of dangerous formula APIs, including 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 family could be identified, but the technique is indicative of a downloader.

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` `7abfcaab2c8427b9f48d0e42860c7a179ff3b67275072dad9dc65b6e48286c4e`	xlm-macro	oletools.olevba.extract_all_macros (XLM macro listing)	6635 bytes

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