Port / TCP
548AFP
Apple Filing Protocol serves Mac file shares and older Time Machine targets on the local network.
If it is internet-facing: Port 548 is legitimate in the right place, but exposed carelessly it widens the attack surface noticeably.
Exposure
Trusted network only
Transport
Encryption optional
Risk if public
Elevated
Exposure verdict
Port 548 belongs on a trusted internal network. If a perimeter scan finds it answering, treat that as a firewall defect rather than a configuration preference.
Encryption is available but negotiated or configured rather than guaranteed. A client that does not insist on it will silently fall back to plaintext.
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 file transfer & shares ports so a rule written for one can be checked against its neighbours.
What actually goes wrong
1 note- Deprecated by Apple in favour of SMB; keep it on the LAN, and prefer 445 for new deployments.
Recommended firewall rule
Allow only from 10.0.0.0/8, drop the rest
Swap in the CIDR your administrators or application tier actually come from — the point is that the default answer is no.
ufw
sudo ufw allow from 10.0.0.0/8 to any port 548 proto tcpiptables
sudo iptables -A INPUT -p tcp -s 10.0.0.0/8 --dport 548 -j ACCEPT
sudo iptables -A INPUT -p tcp --dport 548 -j DROPIf you do need it open to everyone
sudo ufw allow 548/tcpWrite down why. An unexplained allow rule outlives the person who added it, and the next reviewer has no way to tell a deliberate exception from an accident.
Check what is really there
Listening locally
sudo ss -tlpn 'sport = :548'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:548 -sTCP:LISTENmacOS ships lsof rather than ss; this names the owning process and user.
From outside
nmap -sV -Pn -p 548 <host>A version probe confirms whether AFP is actually what answers, rather than trusting the number. Only scan hosts you are authorised to test.
Reachability
nc -vz <host> 548The quick yes/no when you only need to know whether a path exists through the firewall.
The safer path
port 445Move to port 445 — SMB / CIFS
SMB / CIFS 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.