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

Static analysis result for SHA-256 1ffa45b342861069…

MALICIOUS

Office (OLE) / .XLSX

276.0 KB Created: 2006-09-16 00:00:00 Authoring application: Microsoft Excel
MD5: 6249ef10b562faaa194e510223fbc2ef SHA-1: 6fe72201e9084cd867fc968f13bba342e9d41c60 SHA-256: 1ffa45b3428610695d158e716e2bbedaac0168103f1fbbb1bc8cd4f8f950319c
120 Risk Score

Malware Insights

MITRE ATT&CK
T1566.001 Spearphishing Attachment T1204.002 User Execution: Malicious File T1059.005 PowerShell

The sample contains Excel 4.0 macros, including an Auto_Open entry, which are designed to execute automatically when the workbook is opened. It also includes a lure to enable macros by impersonating a signing service. The extracted DOC BODY contains fragmented strings that appear to reconstruct a URL ('www.ottenbourg.com/chester.dll') and commands like 'run' and 'download'. This suggests the macro's purpose is to download and execute a second-stage payload from the specified URL.

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
baa731cba00b83ede600defc492afc68d6365cd3e249e99d81e2ebd1599db0bc
xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 3920 bytes