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Port 48 (auditd)

IANA assigns port 48 to auditd: Digital Audit Daemon.

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

IANA assignment

Service nameProtoDescriptionAssigneeReference
auditd TCP Digital Audit Daemon Larry Scott -
auditd UDP Digital Audit Daemon Larry Scott -

Check what is listening on port 48

Linux: is anything listening on TCP 48?
sudo ss -tlnp 'sport = :48'
Linux: UDP 48
sudo ss -ulnp 'sport = :48'
Linux / macOS: which process owns the port
sudo lsof -nP -i :48
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':48 '
Windows (Command Prompt)
netstat -ano | findstr :48
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 48 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 48
From Windows
Test-NetConnection HOST -Port 48
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 48

Block port 48 in the firewall

ufw
sudo ufw deny 48/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 48 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 48 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 48' -Direction Inbound -Protocol TCP -LocalPort 48 -Action Block
ufw
sudo ufw deny 48/udp
iptables
sudo iptables -A INPUT -p udp --dport 48 -j DROP
nftables
sudo nft add rule inet filter input udp dport 48 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 48' -Direction Inbound -Protocol UDP -LocalPort 48 -Action Block

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