Malicious Office (OLE) / .XLSX — malware analysis report

Static analysis result for SHA-256 81d72825d40254cc…

MALICIOUS

Office (OLE) / .XLSX

36.0 KB Created: 2020-11-27 11:40:20 Authoring application: Microsoft Excel
MD5: a9c3605beb1e8eec8feb5f5b1b096aca SHA-1: 8ae9ddec1f554814553d798fe3ff27c261e8bc46 SHA-256: 81d72825d40254ccd9cfd6921fcc8065ef0fc123b9db80300fb1f5eebdd622e5
140 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1203 Exploitation for Client Execution

The file contains Excel 4.0 macros, specifically an Auto_Open function, which is a critical finding indicating potential malicious execution. The presence of dangerous formula APIs within the macro suggests it is designed to run arbitrary code. This functionality is commonly used to download and execute further malicious payloads, hence the classification as 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.

FilenameKindSourceSize
xlm_macros.txt
f05fde16224584cfe059e2c528e4e2782756d14ab3bab4864cf63818a4bb072a		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6627 bytes

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