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

Static analysis result for SHA-256 010f54e04b889143…

MALICIOUS

Office (OOXML) / .XLSX

16.3 KB Created: 2021-04-27 12:22:10 UTC Authoring application: Microsoft Excel 15.0300
MD5: c86e55a8b8f95aa6877dacb396a29893 SHA-1: a26825bd98fbd04ab30b7c16240088f7b53a9383 SHA-256: 010f54e04b88914349c222fb020f1a02d36ef80ae2d6048df29535d19a2012f8
200 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1059.001 PowerShell T1204.002 Malicious File

The critical heuristic 'OLE_VBA_OBFUSCATED_AUTOEXEC_LOADER' indicates that this OOXML document contains obfuscated VBA code designed to execute automatically upon opening. The 'workbook_open' macro is present, and the script attempts to construct a string using concatenated values from the 'b___v' function, likely to form a command for downloading and executing a payload. The exact nature of the payload is not discernible due to obfuscation and truncation.

Heuristics 5

  • 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
a9a4a4b504268eaafecf4a70dd7d89db69a12a5f830a612aae03412ab8a9cade		 vba-macro oletools.olevba.extract_macros (decoded VBA source from OOXML) 5318 bytes
vbaProject_00.bin
112e15aba9dab05b553afebf9aefa8053fac2997a6566f9be055129ba077eb88		 vba-project OOXML VBA project: xl/vbaProject.bin 22528 bytes

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