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

Static analysis result for SHA-256 5e99709d3967d575…

MALICIOUS

Office (OOXML) / .XLSX

13.7 KB Created: 2020-04-05 18:43:32 UTC Authoring application: Microsoft Excel 16.0300
MD5: 2b21b35b388cf7cf2f36a914f69c6fff SHA-1: 4e40668ee86cb43a39c3ae719be6f1b168aff59d SHA-256: 5e99709d3967d57545d5e42a6f5be9fb4005988ea04642f53fa351cff0f16a13
220 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1059 Command and Scripting Interpreter T1204.002 Malicious File

The file contains a Workbook_Open macro which is a common technique for auto-execution. The macro employs character-shifting and obfuscation to decode and execute a command via the Shell() function, strongly indicating a downloader or dropper behavior. The specific obfuscated string is too complex to fully reconstruct without dynamic analysis, but the intent to execute external code is clear.

Heuristics 5

  • Shell() call in VBA critical OLE_VBA_SHELL
    Shell() call in VBA
  • VBA character-shift decoded Shell command critical OLE_VBA_ASC_CHR_SHIFT_SHELL
    VBA auto-exec macro stores an encoded command string, decodes it with a Mid/Asc/Chr character-shift loop, and passes the recovered text to Shell. This is a high-confidence command stager.
  • Workbook_Open macro high OLE_VBA_WBOPEN
    Workbook_Open macro
  • 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
d4153e2e5a94ec92d26c30402a7df8ba5006bcb71e79fb880364db65ee459f53		 vba-macro oletools.olevba.extract_macros (decoded VBA source from OOXML) 3165 bytes
vbaProject_00.bin
95846cf924a848c0b5728b4e0ff411ebe500f6815f6fff3d2a3a5d105cfe8945		 vba-project OOXML VBA project: xl/vbaProject.bin 15360 bytes

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