Office (OLE) / .XLSX malware analysis — malicious · 2fdab6995533b8e9

MALICIOUS

Office (OLE) / .XLSX

36.0 KB Created: 2020-11-27 11:41:38 Authoring application: Microsoft Excel

MD5: ab9cf96b3c0e5cb93b1dd2d6badba0d2 SHA-1: 2f619c1fa69d431bbb707f6af43c247ca67bedf3 SHA-256: 2fdab6995533b8e916e0c830472ae3db97e89dcffcff676bb0d5b29f0ad7a70b

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 function, which is a critical finding. This indicates the workbook is designed to automatically execute code upon opening. The presence of dangerous formula APIs like RUN further supports the malicious intent. The macro sheet itself contains obfuscated data, suggesting an attempt to hide its true functionality, likely to download and execute a second-stage payload.

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` `e01009ff4cb00bf51cb7595afd9f01ffef7918dfb8a656edc699b30b8c60e210`	xlm-macro	oletools.olevba.extract_all_macros (XLM macro listing)	6595 bytes

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