Jan 23, 2003 · Find out what TCP/IP ports you need to block to secure your network Open TCP/IP ports on your servers can be an invitation to hackers, especially if they're well-known ports such as 21 (FTP), 80

UDP Port 53. Most known and popular usage protocol of DNS is UDP 53. Most DNS servers uses UDP 53 port which provides simplicity and less resource usage. DNSSEC Port Number. DNSSEC provides secure DNS transactions which will secure domain name to IP translation secure manner. DNSSEC can use both UDP and TCP 53 ports. 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. DNS over TLS has its own port, Port 853. DNS over HTTPS uses Port 443, which is the standard port for HTTPS traffic. While having a dedicated port sounds like it would be an advantage, in certain contexts it’s actually quite the opposite. It requires all DNS data be sent on a DNS-over-TLS port. When using TCP Fast Open, the TLS handshake must be initiated immediately. The TLS handshake is process where a TLS connection is negotiated. Adoption depends entirely on the DNS industry.

DoT only uses port 853, while DoH uses port 443, which is the port that all other HTTPS traffic uses as well. Because DoT has a dedicated port, anyone with network visibility can see DoT traffic coming and going, even though the requests and responses themselves are encrypted.

Oct 29, 2019 · The UDP source port is 53 which is the standard port number for unencrypted DNS. The UDP payload is therefore likely to be a DNS answer. That suggests that the source IP address is a DNS resolver while the destination IP is the DNS client.

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Feb 02, 2019 · DNS security issues to avoid. Technically savvy users may utilize Dynamic DNS in combination with OpenVPN, or SSH tunneling to access restricted content and/or bypass security controls on your network. Dynamic DNS itself isn't malicious, but it could be a sign of other problems, absuses or threats to your network's security.