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// Monitoring & logging

Port 4020: TRAP Port

Port 4020 is assigned by IANA to trap (TRAP Port).

4020

How trap works

Monitoring & logging
monitoringdevicetrap monitoringdevicetrap

The monitoring server collects metrics, alerts or logs from devices over port 4020.

Transport
TCP · UDP
Exposure risk
not rated depends on the program listening
Encryption
Unknownnot stated by the registry
IANA status
Assigned1 registered service
Range
Registered (1024-49151)
Category
Monitoring & logging
01 Security

Is port 4020 dangerous?

We have no specific security note for port 4020. Its risk depends on the program actually listening on it. General advice for monitoring & logging services:

  • Restrict management and monitoring protocols to the monitoring network.
  • Replace community strings and default credentials.
  • Send logs over TLS.
02 Registry

IANA registry entries for port 4020

ServicePortTransportDescriptionReferenceUpdated
trap 4020 TCP, UDP TRAP Port - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 4020, and is it reachable?

Linux

sudo ss -ltnup 'sport = :4020'      # process listening on 4020
sudo lsof -nP -i :4020

macOS

sudo lsof -nP -i :4020

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 4020 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 4020
netstat -ano | findstr :4020

From another machine

nmap -p 4020 -sV <host>
sudo nmap -sU -p 4020 <host>
nc -zv <host> 4020

Block it in the firewall

sudo ufw deny 4020/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 4020" -Direction Inbound -LocalPort 4020 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 4020 used for?

Port 4020 is assigned by IANA to trap (TRAP Port).

Is port 4020 TCP or UDP?

Port 4020 is registered for TCP and UDP.

Is it safe to open port 4020?

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. Restrict management and monitoring protocols to the monitoring network.

How do I check if port 4020 is open?

On Linux run "ss -ltnup 'sport = :4020'", on macOS "lsof -nP -i :4020", and on Windows "netstat -ano | findstr :4020" to see the local process. From another machine, "nmap -p 4020 <host>" shows whether it is reachable.

05 Related
:161 SNMP udp · tcp · high risk :162 SNMP trap udp · tcp · moderate risk :9090 Prometheus / admin consoles tcp · udp · high risk :514 Syslog udp · tcp · moderate risk :6514 Syslog over TLS tcp · udp · dccp · low risk :5601 Kibana tcp · udp · high risk :391 SynOptics SNMP Relay Port tcp · udp :412 Trap Convention Port tcp · udp

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