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

Static analysis result for SHA-256 21648b8dd0f5c64c…

MALICIOUS

Office (OLE) / .XLSX

52.5 KB Created: 2015-06-05 18:17:20 Authoring application: Microsoft Excel
MD5: 22d691bde2807f8e68a60cc007e3f42a SHA-1: 2fc4ba15f8d8cec4c4c76f15d7d3c7ea3cab3985 SHA-256: 21648b8dd0f5c64c868ea5bb395eb94b9c462e5b3d4a053c5f81e24858752bc5
160 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic for Applications T1204.002 Malicious File

The sample contains Excel 4.0 macros, including an Auto_Open macro, which is a strong indicator of malicious intent. The document body and heuristics indicate a lure to enable macros. The extracted macro code uses the `REGISTER` function with a URL, suggesting it downloads and executes a second-stage payload. The `ndll32.DllRegisterServer` call further points to the execution of a downloaded component.

Heuristics 4

  • 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.
  • Macro/content-enable lure medium SE_ENABLE_LURE
    Document instructs the user to enable macros or editing — a common technique used by malware droppers to bypass Office macro security settings

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_macros.txt
8509a320b6dbe8e21a7582aae9f5aadecc10d9edb75bf6b48bb45573378d0698
xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 2322 bytes