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

Static analysis result for SHA-256 2b33598b4c6bea00…

MALICIOUS

Office (OLE) / .XLS

36.5 KB Created: 2020-11-25 10:39:30 Authoring application: Microsoft Excel First seen: 2022-02-26
MD5: f4f0b5acd33651cfe58bfd4c9431ae57 SHA-1: 77160f10ad90848d358abe86da95ba2ecf6d3612 SHA-256: 2b33598b4c6bea00c8a9bc7b7478af63c18fe046a9050ff74fb58f15e14b6f67
140 Risk Score

Malware Insights

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

The file is an Excel spreadsheet containing Excel 4.0 macros. A critical heuristic identified an Auto_Open defined name, indicating that macros will execute automatically upon opening the file. The presence of the RUN function within the macro sheet is a strong indicator of malicious intent, likely to execute a command or download a payload. The macro sheet itself contains obfuscated data, but the critical heuristics confirm the use of dangerous functions like RUN.

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
6a5df07b66653d064270a77f7c1451e62e579b58bfe0c75509c3c3c708503094		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6519 bytes

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