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

Static analysis result for SHA-256 98bcde721f139c51…

MALICIOUS

Office (OLE) / .XLSX

115.0 KB Created: 2020-05-20 15:04:03 Authoring application: Microsoft Excel
MD5: a69813244cc896ab41a54ea1b7e395cb SHA-1: 52a5b0e2215d341658197694a87c14342f7cfa64 SHA-256: 98bcde721f139c5134c969bf5a127d4998e7e51838b9da997a34ff8c6178264f
340 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1059.001 PowerShell T1105 Ingress Tool Transfer T1218.005 Signed Binary Proxy Execution: Mshta

The file contains Excel 4.0 macros, specifically an Auto_Open macro, which is a known technique for initial execution. Heuristics indicate the use of ShellExecute and certutil, suggesting the macro is designed to download and decode a secondary payload. The presence of VBA macros further supports the malicious intent. The specific payload or download URL was not directly extracted, but the use of certutil points to a downloader pattern.

Heuristics 8

  • 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.
  • ClamAV: Doc.Downloader.Trojan-bf70f023603538ee-bf70f023603538ee-9950269-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Doc.Downloader.Trojan-bf70f023603538ee-bf70f023603538ee-9950269-0
  • Heap-spray pattern detected high SC_HEAP_SPRAY
    Repeated 0x41 (A) bytes found
  • Reference to ShellExecute API high SC_STR_SHELLEXEC
    Reference to ShellExecute API
  • Reference to certutil (download/decode) high SC_STR_CERTUTIL
    Reference to certutil (download/decode)
  • 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.
  • VBA macros detected medium OLE_VBA_MACROS
    Document contains VBA macro code

Extracted artifacts 2

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_macros.txt
e477e091eb2c093816ecbca0c9d1fa3882851400452ccda2794762f26816afa4		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 5240 bytes
macros.bas
4c946dca4cb780aa1782d34f4c84537d032d4eebef8f341ecfc6f9c5206631fc		 vba-macro oletools.olevba.extract_macros (decoded VBA source) 1104 bytes

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