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

Static analysis result for SHA-256 88a2568a8d57dcb3…

MALICIOUS

Office (OOXML) / .XLSM

436.9 KB Created: 2021-07-28 10:37:27 UTC Authoring application: Microsoft Excel 12.0000
MD5: 3e98190c027b4f07e804c635bc6764d4 SHA-1: 8d5d1d5acb15920e95ee4f523736ea0326f4953b SHA-256: 88a2568a8d57dcb30faacb66e6ddc4de3e9610ad19999b56417b5269f03c0ad8
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, combined with CreateObject and .Exec calls, suggests the script attempts to download and execute a second-stage payload. The reconstructed path 'C:\Users\Public\classic24274.sct' is used to execute the payload via mshta.

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
84c48b5fbfb26d573ca8ececcdafa7acc2e27de8fb7c27a39a3851fd4331e47c		 vba-macro oletools.olevba.extract_macros (decoded VBA source from OOXML) 1148 bytes
vbaProject_00.bin
5f25d1afe78454e77024c9fcf445e6ac56ca1c9240aaa9beae6d261e544048aa		 vba-project OOXML VBA project: xl/vbaProject.bin 9216 bytes

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