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

Static analysis result for SHA-256 00f3a80a1ad8df7a…

MALICIOUS

Office (OLE) / .XLSX

36.0 KB Created: 2020-11-27 11:37:59 Authoring application: Microsoft Excel
MD5: 4f99570436e5d12cdd3e68f6f0f4ff02 SHA-1: e3fa854837f77ed87f62c1a5d59962b298650ab3 SHA-256: 00f3a80a1ad8df7a49d25a8415c837836269aa3e9df51f3848487899a553c0bb
140 Risk Score

Malware Insights

MITRE ATT&CK
T1059 Command and Scripting Interpreter T1059.005 Command and Scripting Interpreter: Visual Basic

The critical heuristics indicate the presence of Excel 4.0 macros with an Auto_Open defined name, which is a known technique for executing malicious code upon opening the spreadsheet. The macro sheet itself contains a large amount of seemingly random data, suggesting obfuscation. The Auto_Open function is designed to run automatically, likely to execute a dangerous formula API such as RUN, which can be used to launch arbitrary commands.

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
c153d860de7ffa7b48424f8d8514570aaf60921b9e0d7a7271a9d23f77c88041
xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6582 bytes