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

Static analysis result for SHA-256 7bc3d12b4bc816fe…

MALICIOUS

Office (OLE) / .XLSX

36.5 KB Created: 2020-11-27 11:42:19 Authoring application: Microsoft Excel
MD5: fe3345ab12cf52f5480486d0088a010c SHA-1: 2eff163a35b7079d19e7020db6267a9fe227b226 SHA-256: 7bc3d12b4bc816fe3463491f0a836f41b6e38a283c2e8a72b80f8d6c38ce8139
140 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1059.001 PowerShell T1566.001 Spearphishing Attachment

The file contains Excel 4.0 macros, specifically an Auto_Open function, which is a known technique for executing malicious code upon opening the document. The critical heuristic firings confirm the presence of dangerous formula APIs like RUN, indicating the macro is designed to execute commands. While the specific payload is not visible, the presence of Auto_Open strongly suggests an intent to download and execute a second-stage payload.

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
4b551019e8f710cdd80b04ecb47402e792ba5b60773630377ba37b0d85291ceb
xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6783 bytes