Port 853: DNS over TLS
Encrypted DNS queries (DoT). Only for resolvers meant to serve the public.
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Port Lookup
Port 853 at a glance
Port853
ProtocolTCP
ServiceDNS over TLS
Open to the Internet?Only to addresses that need it
See What Is Listeningss -lntup | grep ':853 '
Test From Outsidenc -zv your-server 853
Block with UFWufw deny 853/tcp
Block with nftablesnft add rule inet filter input tcp dport 853 drop
DNS over TLS uses TCP port 853. Encrypted DNS queries (DoT).
Only for resolvers meant to serve the public.
Allow port 853 only from the addresses that need it: your office, a VPN or a bastion host. The firewall rule generator builds those rules for nftables, iptables and UFW.
Other Ports
20 FTP Data21 FTP22 SSH23 Telnet25 SMTP53 DNS67 DHCP Server80 HTTP110 POP3123 NTP143 IMAP161 SNMP389 LDAP443 HTTPS445 SMB465 SMTPS514 Syslog587 Mail Submission853 DNS over TLS993 IMAPS995 POP3S1194 OpenVPN1433 Microsoft SQL Server1900 SSDP / UPnP2049 NFS2083 cPanel (SSL)2087 WHM (SSL)3306 MySQL / MariaDB3389 RDP3478 STUN / TURN5060 SIP5432 PostgreSQL5900 VNC6379 Redis8006 Proxmox VE8080 HTTP Alternate8443 HTTPS Alternate11211 Memcached25565 Minecraft27017 MongoDB51820 WireGuard
Questions
What is port 853 used for?
DNS over TLS. Encrypted DNS queries (DoT).
Is it safe to open port 853?
Only to addresses that need it. Only for resolvers meant to serve the public.
How do I check if port 853 is open?
On the server, ss -lntup | grep ':853 ' shows what is listening. From another machine, nc -zv your-server 853 shows whether the firewall lets it through.
How do I block port 853?
With UFW: ufw deny 853/tcp. With nftables, add a drop rule for dport 853 in your input chain.
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