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Port 509 (snare)

IANA assigns port 509 to snare.

Well-known (system) port, 0-1023 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
snare TCP snare Dennis Batchelder -
snare UDP snare Dennis Batchelder -

Check what is listening on port 509

Linux: is anything listening on TCP 509?
sudo ss -tlnp 'sport = :509'
Linux: UDP 509
sudo ss -ulnp 'sport = :509'
Linux / macOS: which process owns the port
sudo lsof -nP -i :509
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':509 '
Windows (Command Prompt)
netstat -ano | findstr :509
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 509 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 509
From Windows
Test-NetConnection HOST -Port 509
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 509

Block port 509 in the firewall

ufw
sudo ufw deny 509/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 509 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 509 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 509' -Direction Inbound -Protocol TCP -LocalPort 509 -Action Block
ufw
sudo ufw deny 509/udp
iptables
sudo iptables -A INPUT -p udp --dport 509 -j DROP
nftables
sudo nft add rule inet filter input udp dport 509 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 509' -Direction Inbound -Protocol UDP -LocalPort 509 -Action Block

Related ports

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All port numbers · Open port checker
Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.