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

Static analysis result for SHA-256 3ffdcb7889fadbe2…

MALICIOUS

Office (OLE) / .XLSX

141.5 KB Created: 2006-09-16 00:00:00 Authoring application: Microsoft Excel
MD5: a1dce5d01333ed3b0a32fe31a07c13c6 SHA-1: 655955fed2381062ce7bf958b1190f9d58e81040 SHA-256: 3ffdcb7889fadbe2ddc08a58ffe81582c6e4dfc28c536cb8ee465efab3ced987
120 Risk Score

Malware Insights

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

The sample contains Excel 4.0 macros with an Auto_Open entry, indicating automatic execution upon opening. It also includes a lure to enable macros by impersonating a document signing service like DocuSign. The embedded URL 'http://bearcatpumps.com.cn/css/tolkio' is likely used to download a second-stage payload. The XLM macro sheet contains obfuscated formulas and references to 'DocuSign', reinforcing the lure.

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.
  • 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
  • Document signing service impersonation lure medium SE_DOCUSIGN_LURE
    Document impersonates DocuSign, Adobe Sign, or a similar signing service in a signing-request context

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_macros.txt
36753cf660f0709fa86ddcbc4a2a70bbd227d5a2ea27f7e28a3b15b989108842		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 2152 bytes

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