- Answer only the networks that need the service (no open resolvers, relays or reflectors).
- UDP services can be abused for DDoS amplification: rate-limit or block them at the edge.
- Disable legacy test services that have no use in production.
Network services ports
DNS, DHCP, NTP, routing, discovery, printing and core infrastructure. 199 ports, most common first.
| Port | Service | Transport | Risk | Encryption |
|---|---|---|---|---|
| 53 | DNS domain | TCP UDP | 4/10 moderate | no |
| 135 | MS RPC epmap | TCP UDP | 8/10 high | no |
| 123 | NTP ntp | UDP TCP | 5/10 moderate | no |
| 67 | DHCP server bootps | UDP TCP | 4/10 moderate | no |
| 111 | rpcbind sunrpc | TCP UDP | 6/10 high | no |
| 9100 | Raw printing (JetDirect) hp-pdl-datastr, pdl-datastream | TCP UDP | 6/10 high | no |
| 631 | IPP / CUPS ipp, ipps | TCP UDP | 6/10 high | optional |
| 5353 | mDNS mdns | UDP TCP | 4/10 moderate | no |
| 5355 | LLMNR llmnr | UDP TCP | 6/10 high | no |
| 137 | NetBIOS Name Service netbios-ns | UDP TCP | 6/10 high | no |
| 1900 | SSDP / UPnP ssdp | UDP TCP | 6/10 high | no |
| 179 | BGP bgp | TCP UDP SCTP | 6/10 high | no |
| 19 | Chargen chargen | UDP TCP | 6/10 high | no |
| 7 | Echo echo | TCP UDP | 4/10 moderate | no |
| 13 | Daytime daytime | TCP UDP | - | - |
| 37 | Time time | TCP UDP | - | - |
| 52 | XNS Time Protocol xns-time | TCP UDP | - | - |
| 63 | whois++ whois++, whoispp | TCP UDP | - | - |
| 79 | Finger finger | TCP UDP | - | - |
| 98 | TAC News tacnews | TCP UDP | - | - |
| 119 | Network News Transfer Protocol nntp | TCP UDP | - | - |
| 138 | NETBIOS Datagram Service netbios-dgm | TCP UDP | - | - |
| 159 | NSS-Routing nss-routing | TCP UDP | - | - |
| 170 | Network PostScript print-srv | TCP UDP | - | - |
| 204 | AppleTalk Echo at-echo | TCP UDP | - | - |
| 386 | ASA Message Router Object Def. asa | TCP UDP | - | - |
| 387 | Appletalk Update-Based Routing Pro. aurp | TCP UDP | - | - |
| 433 | NNTP for transit servers (NNSP) nnsp | TCP UDP | - | - |
| 444 | Simple Network Paging Protocol snpp | TCP UDP | - | - |
| 458 | apple quick time appleqtc | TCP UDP | - | - |
| 515 | spooler printer | TCP UDP | - | - |
| 530 | rpc courier | TCP UDP | - | - |
| 563 | nntp protocol over TLS/SSL (was snntp) nntps | TCP UDP | - | yes |
| 567 | banyan-rpc banyan-rpc | TCP UDP | - | - |
| 581 | Bundle Discovery Protocol bdp | TCP UDP | - | - |
| 647 | DHCP Failover dhcp-failover | TCP UDP | - | - |
| 847 | dhcp-failover 2 dhcp-failover2 | TCP UDP | - | - |
| 853 | DNS query-response protocol run over TLS domain-s | TCP UDP | - | yes |
| 914 | Routing in Fat Trees Link Information Element rift-lies | UDP | - | - |
| 915 | Routing in Fat Trees Topology Information Element rift-ties | UDP | - | - |
| 1035 | MX-XR RPC mxxrlogin | TCP UDP | - | - |
| 1052 | Dynamic DNS Tools ddt | TCP UDP | - | - |
| 1142 | User Discovery Service edtools | TCP UDP | - | - |
| 1198 | cajo reference discovery cajo-discovery | TCP UDP | - | - |
| 1308 | Optical Domain Service Interconnect (ODSI) odsi | TCP UDP | - | - |
| 1337 | menandmice DNS menandmice-dns | TCP UDP | - | - |
| 1392 | Print Manager iclpv-pm | TCP UDP | - | - |
| 1440 | Eicon Service Location Protocol eicon-slp | TCP UDP | - | - |
| 1506 | Universal Time daemon (utcd) utcd | TCP UDP | - | - |
| 1512 | Microsoft's Windows Internet Name Service wins | TCP UDP | - | - |
| 1605 | Salutation Manager (Salutation Protocol) slp | TCP UDP | - | - |
| 1847 | SLP Notification slp-notify | TCP UDP | - | - |
| 1870 | SunSCALAR DNS Service sunscalar-dns | TCP UDP | - | - |
| 1925 | Surrogate Discovery Port discovery-port | TCP UDP | - | - |
| 1985 | Hot Standby Router Protocol hsrp | TCP UDP | - | - |
| 1997 | cisco Gateway Discovery Protocol gdp-port | TCP UDP | - | - |
| 2009 | news, whosockami | TCP UDP | - | - |
| 2029 | Hot Standby Router Protocol IPv6 hsrpv6 | TCP UDP | - | - |
| 2079 | IDWARE Router Port idware-router | TCP UDP | - | - |
| 2164 | Dynamic DNS Version 3 ddns-v3 | TCP UDP | - | - |
| 2291 | EPSON Advanced Printer Share Protocol eapsp | TCP UDP | - | - |
| 2374 | Hydra RPC hydra | TCP | - | - |
| 2428 | One Way Trip Time ott | TCP UDP | - | - |
| 2514 | Facsys NTP facsys-ntp | TCP UDP | - | - |
| 2515 | Facsys Router facsys-router | TCP UDP | - | - |
| 2599 | Snap Discovery snapd | TCP UDP | - | - |
| 3096 | Active Print Server Port ndl-aps | TCP UDP | - | - |
| 3129 | NetPort Discovery Port netport-id | TCP UDP | - | - |
| 3224 | AES Discovery Port aes-discovery | TCP UDP | - | - |
| 3318 | Swith to Swith Routing Information Protocol ssrip | TCP UDP | - | - |
| 3347 | Phoenix RPC phoenix-rpc | TCP UDP | - | - |
| 3396 | Printer Agent printer_agent, printer-agent | TCP UDP | - | - |
| 3446 | 3Com FAX RPC port 3comfaxrpc | TCP UDP | - | - |
| 3448 | Discovery and Net Config dnc-port | TCP UDP | - | - |
| 3479 | 2Wire RPC twrpc | TCP UDP | - | - |
| 3502 | Avocent Install Discovery avinstalldisc | TCP UDP | - | - |
| 3503 | MPLS LSP-echo Port lsp-ping | TCP UDP | - | - |
| 3553 | Red Box Recorder ADP rbr-discovery | TCP UDP | - | - |
| 3613 | Alaris Device Discovery alaris-disc | TCP UDP | - | - |
| 3623 | HAIPIS Dynamic Discovery haipe-discover | TCP UDP | - | - |
| 3706 | Real-Time Event Port rt-event | TCP UDP | - | - |
| 3707 | Real-Time Event Secure Port rt-event-s | TCP UDP | - | - |
| 3764 | MNI Protected Routing mni-prot-rout | TCP UDP | - | - |
| 3785 | BFD Echo Protocol bfd-echo | TCP UDP | - | - |
| 3788 | SPACEWAY Routing port isrp-port | TCP UDP | - | - |
| 3800 | Print Services Interface pwgpsi | TCP UDP | - | - |
| 3819 | EPL Sequ Layer Protocol epl-slp | TCP UDP | - | - |
| 3822 | Compute Pool Discovery acp-discovery | TCP UDP | - | - |
| 3837 | MARKEM Auto-Discovery mkm-discovery | TCP UDP | - | - |
| 3849 | SPACEWAY DNS Preload spw-dnspreload | TCP UDP | - | - |
| 3861 | winShadow Host Discovery winshadow-hd | TCP UDP | - | - |
| 3910 | Printer Request Port prnrequest | TCP UDP | - | - |
| 3911 | Printer Status Port prnstatus | TCP UDP | - | - |
| 3937 | DVB Service Discovery dvbservdsc | TCP UDP | - | - |
| 3949 | Dynamic Routing Information Protocol drip | TCP UDP | - | - |
| 3951 | PWG IPP Facsimile pwgippfax | TCP UDP | - | - |
| 3954 | AD Replication RPC adrep | TCP UDP | - | - |
| 3963 | Teran Hybrid Routing Protocol thrp | TCP UDP | - | - |
| 4063 | Ice Firewall Traversal Service (TCP) ice-router | TCP UDP | - | - |
| 4126 | Data Domain Replication Service ddrepl | TCP UDP | - | - |
Securing network services services
Other port categories
Web /tools/ports/category/web Remote access /tools/ports/category/remote-access File transfer & sharing /tools/ports/category/file-transfer Email /tools/ports/category/email Databases & caches /tools/ports/category/databases Directory & authentication /tools/ports/category/directory-auth VPN, tunnels & proxies /tools/ports/category/vpn-tunnels Messaging & queues /tools/ports/category/messaging Voice & chat /tools/ports/category/voice-chat Media & streaming /tools/ports/category/media IoT & industrial (ICS) /tools/ports/category/iot-ics DevOps, cloud & containers /tools/ports/category/devops Monitoring & logging /tools/ports/category/monitoring Gaming /tools/ports/category/gaming Other services /tools/ports/category/other