Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 c64c00fd108d4710…

MALICIOUS

Office (OOXML)

215.5 KB Created: 2021-07-14 10:33:49 UTC Authoring application: Microsoft Excel 15.0300
MD5: e9010d4f82a4efb25e00b21c16e48b2b SHA-1: f85c70b2a395c77917d8898d97717b3a18e5b341 SHA-256: c64c00fd108d4710ab822253a11913379ccc148160c8440a0ad3c96979a8706d
320 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1204.002 Malicious File T1140 Deobfuscate/Decode Files or Information

The sample is an Excel document containing a Workbook_Open macro that calls an obfuscated VBA function. This function appears to be designed to download and execute a second-stage payload, as indicated by the critical heuristics for Shell() calls, WScript.Shell usage, and obfuscated auto-exec loaders. The VBA code uses string concatenation to build commands, likely for downloading and executing further malicious content.

Heuristics 7

  • Shell() call in VBA critical OLE_VBA_SHELL
    Shell() call in VBA
  • WScript.Shell usage critical OLE_VBA_WSCRIPT
    WScript.Shell usage
  • 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

Extracted artifacts 2

Files carved from inside the sample during analysis.

FilenameKindSourceSize
macros.bas
cdd9535c4ec625dbcdd5fcf5e63eb5d1373c0f87dbf41f48797c3e563d84961a		 vba-macro oletools.olevba.extract_macros (decoded VBA source from OOXML) 2797 bytes
vbaProject_00.bin
5a8d24959845b64ca0322d04ec9867d9bb9415448916cf969490690592af1f54		 vba-project OOXML VBA project: xl/vbaProject.bin 18944 bytes

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