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

Static analysis result for SHA-256 1fa2c04b79c5100d…

MALICIOUS

Office (OLE) / .XLSX

36.5 KB Created: 2020-11-25 10:42:06 Authoring application: Microsoft Excel
MD5: edae7feffe555c0a0caa00d77783d3f8 SHA-1: e697a7cf39f71e7f26e00712e5fbae876e11166d SHA-256: 1fa2c04b79c5100d1c39b74dea8627314362904da195d239a8c989684f34ae7f
140 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1059.001 PowerShell T1204.002 Malicious File

The file is an Excel 4.0 macro-enabled workbook. Heuristics indicate the presence of an Auto_Open macro, which is a common technique for executing malicious code upon opening the document. The macro sheet contains a defined name 'Auto_Open' and uses dangerous formula APIs, specifically the RUN function, to execute arbitrary commands. The document body contains obfuscated strings that are likely part of the macro's execution flow or payload. The primary IOC is the sheet name 'STRXErP' which is associated with the macro execution.

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
a90781d7bf2774422f8c9210be43ead5ca571aa9bb2a5151d756527af4ff3cdc
xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6523 bytes