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// Other services

Port 520: extended file name server

Port 520 is assigned by IANA to efs (extended file name server), router (local routing process (on site); uses variant of Xerox NS routing information protocol - RIP).

520

How efs works

Other services
client:520efsresponse client:520efsresponse

The client sends a request to port 520 and the efs service answers.

Transport
TCP · UDP
Exposure risk
not rated depends on the program listening
Encryption
Unknownnot stated by the registry
IANA status
Assigned2 registered services
Range
Well-known (0-1023)
Category
Other services
01 Security

Is port 520 dangerous?

We have no specific security note for port 520. Its risk depends on the program actually listening on it. General advice for other services services:

  • Close the port if nothing on the host needs it.
  • Identify the process that listens on it (commands below) before opening it in a firewall.
  • Expose a service only to the networks that use it.
02 Registry

IANA registry entries for port 520

ServicePortTransportDescriptionReferenceUpdated
efs 520 TCP extended file name server - -
router 520 UDP local routing process (on site); uses variant of Xerox NS routing information protocol - RIP - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 520, and is it reachable?

Linux

sudo ss -ltnup 'sport = :520'      # process listening on 520
sudo lsof -nP -i :520

macOS

sudo lsof -nP -i :520

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 520 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 520
netstat -ano | findstr :520

From another machine

nmap -p 520 -sV <host>
sudo nmap -sU -p 520 <host>
nc -zv <host> 520

Block it in the firewall

sudo ufw deny 520/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 520" -Direction Inbound -LocalPort 520 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 520 used for?

Port 520 is assigned by IANA to efs (extended file name server), router (local routing process (on site); uses variant of Xerox NS routing information protocol - RIP).

Is port 520 TCP or UDP?

Port 520 is registered for TCP and UDP.

Is it safe to open port 520?

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. Close the port if nothing on the host needs it.

How do I check if port 520 is open?

On Linux run "ss -ltnup 'sport = :520'", on macOS "lsof -nP -i :520", and on Windows "netstat -ano | findstr :520" to see the local process. From another machine, "nmap -p 520 <host>" shows whether it is reachable.

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