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

Static analysis result for SHA-256 ff6d5af8b24b7b23…

MALICIOUS

Office (OLE) / .XLSX

70.5 KB Created: 2015-06-05 18:19:34 Authoring application: Microsoft Excel First seen: 2022-05-27
MD5: 5599c93a7870ea2270452d6a39c69348 SHA-1: 1b5e59fb283aba363dc3cda2221d9be1e4056b5a SHA-256: ff6d5af8b24b7b230895ea480426cafbfddc0ebc1db440b741b2d740f7efd639
140 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic for Applications T1204.002 Malicious File

The file contains Excel 4.0 macros, specifically an Auto_Open function, which is a critical finding. This function is designed to execute automatically upon opening the workbook. The macros also contain references to dangerous formula APIs, including the RUN function, indicating an intent to execute external code. The extracted URLs are likely used to download and execute a second-stage payload. The presence of the Auto_Open macro and the use of the RUN function strongly suggest a downloader or droppper attack pattern.

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
699e21f010c7c5f5713063f52e691ec519f766e81393f8793f7a585cd43d5349
xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 7635 bytes