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

Static analysis result for SHA-256 31a4b12c984025a4…

MALICIOUS

Office (OLE) / .XLSX

36.0 KB Created: 2020-11-27 11:43:43 Authoring application: Microsoft Excel
MD5: b9427335bb6124043b89cf94f8d4e3f3 SHA-1: b525a84506e8bd66d86df6ccf1d545e5454af64e SHA-256: 31a4b12c984025a4e0cbe8d9729cc9bcc84e65411ddf8bee8d1ba6dd10d9e9bc
140 Risk Score

Malware Insights

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

The file contains Excel 4.0 macros, specifically an Auto_Open function, which is a critical finding. This function is known to be used for executing arbitrary commands. The presence of the 'RUN' function within the macro sheet indicates an intent to execute external commands, likely for downloading and executing a secondary payload. The heuristics strongly suggest malicious intent, and the Auto_Open macro is the primary mechanism for this.

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
89aae28e7515cce45e8723c50591d86b7479c2bd5b5e20ccc34ecc9b10da56bb
xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6618 bytes