Malicious Office (OLE) — malware analysis report

Static analysis result for SHA-256 fdd4ee9e0e1f197e…

MALICIOUS

Office (OLE)

315.5 KB Created: 2018-07-26 00:26:51 Authoring application: Microsoft Excel
MD5: 5d15ccd61fa8f1488c26d0d4e39904dd SHA-1: 40eeb9943f5af7f3e81c1b1a628919dd47be973e SHA-256: fdd4ee9e0e1f197e66f1efae2ce26db6ef0a1fa0867f9316c3cdb288fff6690f
288 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1203 Exploitation for Client Execution

The sample is an Excel file containing an obfuscated Workbook_Open VBA macro. This macro uses CreateObject to write a script file named '//klWK1ALL.sct' to disk and then executes it using mshta.exe via Wscript.Shell. The script itself is too obfuscated to fully analyze, but the presence of mshta.exe and Wscript.Shell indicates a likely download and execution of a second-stage payload.

Heuristics 8

  • 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.
  • Reference to Windows Script Host high SC_STR_WSCRIPT
    Reference to Windows Script Host
  • Reference to mshta.exe high SC_STR_MSHTA
    Reference to mshta.exe
  • 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
517083b7d22a975b75685066598355ddb9eb65d6ce793f78d437a03f1a0a0b69		 vba-macro oletools.olevba.extract_macros (decoded VBA source) 1176 bytes

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