Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 c866ce5c6646fe61…

MALICIOUS

Office (OOXML)

435.3 KB Created: 2021-07-28 10:37:27 UTC Authoring application: Microsoft Excel 12.0000
MD5: f8834b526ab81b970cbd94cea38dfad0 SHA-1: d0febbe464b56e56681b12dd3902778360d9543e SHA-256: c866ce5c6646fe615a4a9abe7295469efb7bab7e7e2181a75ee95d70808064dc
208 Risk Score

Malware Insights

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

The critical heuristic 'OLE_VBA_OBFUSCATED_AUTOEXEC_LOADER' indicates an obfuscated auto-exec VBA loader. The WorkBook_Open macro constructs a path using Environ and Cells values, which resolves to 'ALLUSERSPROFILE\getCGM0808.sct'. It then uses CreateObject to execute this file via mshta, likely downloading and running a second-stage payload.

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
16561381310e8781e32d055f8361960019878a92bbbf5011b66b99e81f0e16c1		 vba-macro oletools.olevba.extract_macros (decoded VBA source from OOXML) 1117 bytes
vbaProject_00.bin
a77808b125d6d7f6b62e97348f8ea910404048a674862336fae8fbeda5c69809		 vba-project OOXML VBA project: xl/vbaProject.bin 9216 bytes

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