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

Static analysis result for SHA-256 d55ac109967ad7ba…

MALICIOUS

Office (OLE) / .XLS

36.0 KB Created: 2020-11-25 10:38:12 Authoring application: Microsoft Excel First seen: 2022-04-23
MD5: a3c5dbb91db79048051b10c1164912c7 SHA-1: 6b589814ac3f42e105bdbacfa5a737856c9a2d12 SHA-256: d55ac109967ad7ba845f8355192ef69a8ffd5a0e1038fbb94e75f974ca569246
140 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic for Applications T1059.001 PowerShell T1059.003 Windows Command Shell

The sample is an Excel 4.0 (XLM) macro-enabled spreadsheet. Heuristics indicate the presence of an Auto_Open defined name, which is a common technique for automatic execution upon opening the file. The XLM macro sheet contains a call to the RUN function, which is a dangerous API used to execute arbitrary commands. This suggests the macro is designed 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.

FilenameKindSourceSize
xlm_macros.txt
26b39e5579216f02cd5d41f9bbd5215ed886a4385e84749dbfe5a485af592cfa
xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6602 bytes