Security practitioners for decades have advised people to limit DNS queries against their DNS servers to only use UDP port 53. The reality is that DNS queries can also use TCP port 53 if UDP port
outbound port 53/UDP (DNS) used for DNS lookups converting hostnames to IP addresses local port 80/TCP (HTTP) : local access to the built-in Web UI of the VidiU for configuration and stream control, as described in this article Port(s) FortiManager v3.0: FortiGuard Web Filtering and Antispam rating replies: Source: UDP 53 (default) or UDP 8888 Destination: UDP 1027 or UDP 1031: FortiOS v3.0: FortiGuard Web Filtering and Antispam rating lookup This can be to the FDN or to a FortiManager acting as a private FDS. Source: UDP 1027 or 1031 Destination: UDP 53 (default) or Some Known UDP Port: Here are 3 known UDP Port that you can check using out UDP Port Checker tool. 53 – Domain Name System (DNS). 67 – Dynamic Host Configuration Protocol (DHCP) and Bootstrap Protocol (BOOTP) server; 111 – Open Network Computing Remote Procedure Call (RCP). Aug 25, 2016 · TCP port 22 – OpenSSH (remote) secure shell server; TCP port 110 – POP3 (Post Office Protocol v3) server; TCP port 143 – Internet Message Access Protocol (IMAP) — management of email messages; TCP / UDP port 53 – Domain Name System (DNS) Block Incoming Port. The syntax is as follows to block incoming port using IPtables: Solved: I have what I believe to be an easy question. I want to lock down port 53 for outbound access to 3 of our internal DNS servers so that they're the only hosts that can service requests in the outbound direction. TCP/UDP port 53 for DNS offers an exit strategy. Once criminal hackers inside the network have their prize, all they need to do to get it out the door is use readily available software that turns
You can tunnel IP over pretty much any of the common application protocols, not to mention TLS, so that's hardly a good reason for dropping traffic. Besides, you would think an IP-over-DNS scheme would bind to an ephemeral port client-side (like regular DNS clients do), rather than port 53. – Blacklight Shining Feb 12 '16 at 6:19
The answer is DNS is mostly UDP Port 53, but as time progresses, DNS will rely on TCP Port 53 more heavily. DNS has always been designed to use both UDP and TCP port 53 from the start 1, with UDP being the default, and fall back to using TCP when it is unable to communicate on UDP, typically when the packet size is too large to push through in a single UDP packet. Security practitioners for decades have advised people to limit DNS queries against their DNS servers to only use UDP port 53. The reality is that DNS queries can also use TCP port 53 if UDP port Guaranteed communication over port 53 is the key difference between TCP and UDP. UDP port 53 would not have guaranteed communication in the same way as TCP. Because protocol TCP port 53 was flagged as a virus (colored red) does not mean that a virus is using port 53, but that a Trojan or Virus has used this port in the past to communicate. TCP
Here is a short post to check port [TCP/UDP] connectivity from a Linux server. A TCP/IP network connection may be either blocked, dropped, open, or filtered. These actions are generally controlled by the IPtables firewall the system uses and is independent of any process or program that may be listening on a network port.
Sep 21, 2012 · Windows XP and/or Windows Server 2003 may be unexpectedly listening on UDP Port 53 and/or even responding to DNS queries. netstat -aon | find ":53 "shows UDP 192.168.0.1:53 *:* 1234 Where 1234 is the process ID being used for svchost session for SharedAccess service.