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

Static analysis result for SHA-256 1f3c5dd0a79323c5…

MALICIOUS

Office (OLE) / .XLSX

32.0 KB Created: 2022-04-12 16:40:38 Authoring application: Microsoft Excel First seen: 2022-09-14
MD5: b12fce712eeaf19f3982c9d6d3b1496c SHA-1: 5ca0edba3e946291b9ce3be3758c434250c074e6 SHA-256: 1f3c5dd0a79323c57ad194a49eebaaf2f624822df401995e51a4c58b5a607a45
328 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1059.001 PowerShell T1105 Ingress Tool Transfer T1204.002 Malicious File

The Workbook_Open macro is obfuscated and uses CreateObject and Shell calls to download a file from http://168.100.8.42/cr.exe and save it as putty.exe in the user's AppData directory. It then executes the downloaded file, indicating a downloader or dropper functionality.

Heuristics 8

  • Shell() call in VBA critical OLE_VBA_SHELL
    Shell() call in VBA
  • VBA downloads and writes a file to disk critical OLE_VBA_HTTP_DROP_EXEC
    VBA reads an HTTP response body and writes it to disk (ADODB.Stream SaveToFile). Combined with the auto-exec/Shell paths this is a download-drop dropper even when the COM ProgIDs are built dynamically to evade keyword scanning.
  • Obfuscated auto-exec VBA loader critical OLE_VBA_OBFUSCATED_AUTOEXEC_LOADER
    Auto-exec VBA reconstructs strings with a heavy custom decoder (numeric char-array, repeated hex-string decode, or junk-token Replace removal) and feeds them to a COM-instantiation or execution sink. This obfuscated-loader shape keeps CreateObject/Shell/URL indicators out of the macro source.
  • Workbook_Open macro high OLE_VBA_WBOPEN
    Workbook_Open macro
  • CreateObject call high OLE_VBA_CREATEOBJ
    CreateObject call
  • VBA p-code auto-exec with execution tokens high OLE_VBA_PCODE_AUTOEXEC_EXEC
    Compiled VBA/cache stream contains an auto-execution token together with shell/download/object-execution tokens. This catches p-code-only or source-extraction-failure macro documents where visible source is unavailable.
  • VBA macros detected medium OLE_VBA_MACROS
    Document contains VBA macro code
  • Environ() call (env variable access) low OLE_VBA_ENVIRON
    Environ() call (env variable access)

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
macros.bas
028da731e6ecbc26ac90379137b6530193ef4fc6b7430bd11b0f4456a42b1c44		 vba-macro oletools.olevba.extract_macros (decoded VBA source) 1704 bytes

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