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

Static analysis result for SHA-256 29a0779fb3329f11…

MALICIOUS

Office (OLE) / .XLSX

36.5 KB Created: 2020-11-25 10:44:49 Authoring application: Microsoft Excel
MD5: 51078e95ecbe7f3972b1555931e5d5d5 SHA-1: 491c23c2ce28fbd73ee0168324a627dfe9ee1902 SHA-256: 29a0779fb3329f11c5df4c3672eab7c6ea4cd109f37a59fa885c949075ed3eb2
140 Risk Score

Malware Insights

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

The file contains Excel 4.0 macros, specifically an Auto_Open defined name, which is a critical finding. This indicates the workbook is designed to automatically execute code upon opening. The presence of 'RUN' as a dangerous formula API suggests the macro is capable of executing arbitrary commands, likely to download and run a second-stage payload. No specific family could be identified, but the technique is common for initial access.

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
327b87c7394aeef2c132b420a85f1b435dd72d0fadc15b07184055d4990ae5d4
xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6508 bytes