Port / TCP
80HTTP
HTTP serves unencrypted web traffic; on modern sites it mostly exists to redirect to HTTPS and to answer ACME challenges.
If it is internet-facing: Port 80 is legitimate in the right place, but exposed carelessly it widens the attack surface noticeably.
Exposure
Internet-facing
Transport
Cleartext
Risk if public
Elevated
Exposure verdict
Port 80 normally answers from the internet, but the transport is not confidential by default. Enforce the encrypted variant before the traffic leaves your network.
Traffic crosses the network readable and modifiable. Anything sensitive on this port needs a tunnel, a VPN, or a different protocol.
Assigned by IANA through a review process. On Unix systems a process needs root or the CAP_NET_BIND_SERVICE capability to bind here, which is why containers so often remap these to a higher port.
Grouped with the other web & proxies ports so a rule written for one can be checked against its neighbours.
What actually goes wrong
2 notes- Anything sent before the redirect — cookies, form posts, the URL itself — is readable on the wire.
- HSTS with a preload entry is what stops the first plaintext request from happening at all.
Recommended firewall rule
Allow it, and harden the service
This port is expected to answer from anywhere, so the firewall is not where its security comes from.
ufw
sudo ufw allow 80/tcpiptables
sudo iptables -A INPUT -p tcp --dport 80 -j ACCEPTCheck what is really there
Listening locally
sudo ss -tlpn 'sport = :80'The bind address is the answer that matters: 127.0.0.1 is local-only, 0.0.0.0 and :: mean every interface.
Listening (macOS)
sudo lsof -nP -iTCP:80 -sTCP:LISTENmacOS ships lsof rather than ss; this names the owning process and user.
From outside
nmap -sV -Pn -p 80 <host>A version probe confirms whether HTTP is actually what answers, rather than trusting the number. Only scan hosts you are authorised to test.
Reachability
nc -vz <host> 80The quick yes/no when you only need to know whether a path exists through the firewall.
The safer path
port 443Move to port 443 — HTTPS
HTTPS does the same job with the session protected from the first byte, so there is no plaintext phase for an on-path attacker to read or strip. Migrating is usually a client configuration change plus a firewall swap.