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

Static analysis result for SHA-256 2087072711881a08…

MALICIOUS

Office (OLE) / .XLSX

214.5 KB Created: 2020-05-29 06:33:16 Authoring application: Microsoft Excel
MD5: f6bd17a313a73d70672efa852d84c5c1 SHA-1: 71ecd121b047bf1d83bdb460eef4c107e03ba228 SHA-256: 2087072711881a088bdbb1c6c669f3221a09b8ca0e681e7957eb9e980cc4cd5f
140 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic

The file contains an Excel 4.0 macro sheet with an Auto_Open entry, which is a known technique for automatic execution upon opening. The macros are heavily obfuscated using CHAR() functions and arithmetic operations, making it difficult to determine the exact payload. The presence of a RUN command suggests the execution of an external program or script. The obfuscation and auto-execution chain indicate a malicious intent to run arbitrary code.

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
d780f6fe0233b0c3c8cce9401bfae6b98f8a8520ce585c730531fdd19b1a0efa
xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 125867 bytes