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

Static analysis result for SHA-256 3efcb54fa0068d11…

MALICIOUS

Office (OLE) / .XLSX

320.5 KB Created: 2020-05-20 11:19:40 Authoring application: Microsoft Excel
MD5: 734336dbe950e709b8af121aedcca34a SHA-1: 8cc96a0fc66cc13b89dc152dc6ba32c3fff6125f SHA-256: 3efcb54fa0068d11f481d81539dd624faa1525e6839c4b7b38c96e6ff1b7c13a
140 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic for Applications T1059.001 PowerShell

The file contains critical heuristics indicating the presence of obfuscated Excel 4.0 macros designed for auto-execution. The 'OLE_XLM_OBFUSCATED_AUTOEXEC_CHAIN' firing suggests a chain of commands, including 'RUN', 'FORMULA(CHAR)', and 'risky-formula', which are commonly used to download and execute a second-stage payload. The macro sheet itself is extensive, but the specific execution chain is obfuscated, preventing a precise reconstruction of the payload delivery mechanism.

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.
  • Obfuscated XLM Auto_Open execution chain critical OLE_XLM_OBFUSCATED_AUTOEXEC_CHAIN
    Excel 4.0 macro sheet contains an Auto_Open / Auto_Close entry and an obfuscated formula execution chain. The macro builds strings through FORMULA(CHAR(...)), primes state with SET.VALUE / GET.CELL / GOTO, and transfers control through RUN(). This is a high-confidence XLM malware pattern.
  • 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
68818120d2c965d3c782b84f488488984cc175c0fdb44f0e6f57d2777709989c
xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 127172 bytes