Is port 53 a vulnerability?

Vulnerabilities in DNS Bypass Firewall Rules (UDP 53) is a Low risk vulnerability that is also high frequency and high visibility. This is the most severe combination of security factors that exists and it is extremely important to find it on your network and fix it as soon as possible.

Is UDP port 53 secure?

The DNS protocol – operating on UDP port 53 for normal requests – is used as a means of “tunnelling” through security systems to steal data. The channel is not normally used for sending information and so is not always monitored by security systems.

What ports are vulnerable?

Commonly Hacked Ports

TCP port 21 — FTP (File Transfer Protocol)
TCP port 22 — SSH (Secure Shell)
TCP port 23 — Telnet.
TCP port 25 — SMTP (Simple Mail Transfer Protocol)
TCP and UDP port 53 — DNS (Domain Name System)
TCP port 443 — HTTP (Hypertext Transport Protocol) and HTTPS (HTTP over SSL)

What is listening on port 53?

Port 53 is reserved for the Domain Name System (DNS). In your case it is the DNS cacher dnsmasq of the package dnsmasq-base . This pre-installed package is a dependency of network-manager , the network manager of your desktop environment (e.g. Unity, GNOME, …).

What is the purpose of port 53?

DNS uses Port 53 which is nearly always open on systems, firewalls, and clients to transmit DNS queries. Rather than the more familiar Transmission Control Protocol (TCP) these queries use User Datagram Protocol (UDP) because of its low-latency, bandwidth and resource usage compared TCP-equivalent queries.

Why is port 53 blocked?

Zone transfers take place over TCP port 53 and in order to prevent our DNS servers from divulging critical information to attackers, TCP port 53 is typically blocked.

Which ports should never be open?

Ports restricted even from UI networks

Port 123: NTP UDP. Blocked: In to unapproved servers. This port is associated with NTP, the network time protocol.
Ports 161 UDP-162 TCP/UDP: SNMP. Blocked: Inbound.
Ports 1434 UDP and 41170 UDP: Denial of service file sharing. Blocked: Both in and out.

How can I get free port 53?

0.0:53: bind: address already in use”….This is what you must do.

Start by editing /etc/systemd/resolved.conf with a text editor (as root), e.g. open it with Nano console text editor: sudo nano /etc/systemd/resolved.conf.
Remove the /etc/resolv.conf symbolic link: sudo rm /etc/resolv.conf.
Reboot your system.

Do you need port 53 open?

Port 53 is open for DNS. Why would I need this? You need to have UDP 53 allowed for responses to DNS queries that your server sends, as UDP is a stateless protocol. Don’t block it if you want any kind of outbound connectivity, software updates, etc.