- Patch VPN gateways quickly: they are a top initial access target.
- Use certificates or MFA rather than shared secrets.
- Investigate unexpected tunnels and proxies: they are also attacker tools.
Port 604: TUNNEL
Port 604 is assigned by IANA to tunnel (TUNNEL).
604
How tunnel works
VPN, tunnels & proxiesTraffic is wrapped in a tunnel between the two ends, so the network in between only sees the tunnel.
- Transport
- TCP · UDP
- Exposure risk
- not rated depends on the program listening
- Encryption
- Unknownnot stated by the registry
- IANA status
- Assigned1 registered service
- Range
- Well-known (0-1023)
- Category
- VPN, tunnels & proxies
Is port 604 dangerous?
We have no specific security note for port 604. Its risk depends on the program actually listening on it. General advice for vpn, tunnels & proxies services:
IANA registry entries for port 604
| Service | Port | Transport | Description | Reference | Updated |
|---|---|---|---|---|---|
| tunnel | 604 | TCP, UDP | TUNNEL | RFC 3620 | - |
// source: IANA service name and port number registry
Which program uses port 604, and is it reachable?
Linux
sudo ss -ltnup 'sport = :604' # process listening on 604
sudo lsof -nP -i :604macOS
sudo lsof -nP -i :604
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 604 -State Listen | Select LocalAddress, OwningProcess Get-NetUDPEndpoint -LocalPort 604 netstat -ano | findstr :604
From another machine
nmap -p 604 -sV <host> sudo nmap -sU -p 604 <host> nc -zv <host> 604
Block it in the firewall
sudo ufw deny 604/tcp # Linux (ufw) New-NetFirewallRule -DisplayName "Block 604" -Direction Inbound -LocalPort 604 -Protocol TCP -Action Block # Windows
What is port 604 used for?
Port 604 is assigned by IANA to tunnel (TUNNEL).
Is port 604 TCP or UDP?
Port 604 is registered for TCP and UDP.
Is it safe to open port 604?
It depends on the program that listens on it. Open it only for a service you know and only to the networks that need it. Patch VPN gateways quickly: they are a top initial access target.
How do I check if port 604 is open?
On Linux run "ss -ltnup 'sport = :604'", on macOS "lsof -nP -i :604", and on Windows "netstat -ano | findstr :604" to see the local process. From another machine, "nmap -p 604 <host>" shows whether it is reachable.