Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 81a5b774a7957f4d…

MALICIOUS

Office (OOXML)

435.5 KB Created: 2021-07-28 10:37:27 UTC Authoring application: Microsoft Excel 12.0000
MD5: 5e6325d5c6ce9c1a12d4923b01798453 SHA-1: 31de6f4ab3a4b2d7a488fc9e3cf23841e023df81 SHA-256: 81a5b774a7957f4db951c15e1d69407b5879380d0bc52ee96fc9e9312bd46a8a
208 Risk Score

Malware Insights

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

The sample is an Excel document containing an obfuscated Workbook_Open VBA macro. This macro uses CreateObject to execute a script file, 'C:\Users\Public\getIMEModeNoControl0359.sct', via mshta. The script itself is likely responsible for downloading and executing a second-stage payload, indicated by the use of Environ() and CreateObject calls within the VBA code.

Heuristics 6

  • 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 project inside OOXML medium OOXML_VBA
    Document contains a VBA project — VBA macros present
  • Environ() call (env variable access) low OLE_VBA_ENVIRON
    Environ() call (env variable access)

Extracted artifacts 2

Files carved from inside the sample during analysis.

FilenameKindSourceSize
macros.bas
fa2c7e5bf2af02b46130006e76148b8f39b2b09e83ecc4fde15081e7c79cab5e		 vba-macro oletools.olevba.extract_macros (decoded VBA source from OOXML) 1141 bytes
vbaProject_00.bin
5abed9c6efbf87ee9d311c7084118ee0a7c463db7e52629eba74ca2e22fef091		 vba-project OOXML VBA project: xl/vbaProject.bin 9216 bytes

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