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// File transfer & sharing

Port 4687: Network Scanner Tool FTP

Port 4687 is assigned by IANA to nst (Network Scanner Tool FTP).

4687

How nst works

File transfer & sharing
client:46871/32/33/3nst client:46871/32/33/3nst

Files are sent over port 4687 in pieces and reassembled on the other side.

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
File transfer & sharing
01 Security

Is port 4687 dangerous?

We have no specific security note for port 4687. Its risk depends on the program actually listening on it. General advice for file transfer & sharing services:

  • Prefer encrypted protocols (SFTP, FTPS, SMB 3 with encryption).
  • Disable anonymous access and restrict shares or exports to known hosts.
  • Never publish file sharing protocols to the Internet.
02 Registry

IANA registry entries for port 4687

ServicePortTransportDescriptionReferenceUpdated
nst 4687 TCP, UDP Network Scanner Tool FTP - 2005-08

// source: IANA service name and port number registry

03 Check it

Which program uses port 4687, and is it reachable?

Linux

sudo ss -ltnup 'sport = :4687'      # process listening on 4687
sudo lsof -nP -i :4687

macOS

sudo lsof -nP -i :4687

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 4687 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 4687
netstat -ano | findstr :4687

From another machine

nmap -p 4687 -sV <host>
sudo nmap -sU -p 4687 <host>
nc -zv <host> 4687

Block it in the firewall

sudo ufw deny 4687/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 4687" -Direction Inbound -LocalPort 4687 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 4687 used for?

Port 4687 is assigned by IANA to nst (Network Scanner Tool FTP).

Is port 4687 TCP or UDP?

Port 4687 is registered for TCP and UDP.

Is it safe to open port 4687?

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. Prefer encrypted protocols (SFTP, FTPS, SMB 3 with encryption).

How do I check if port 4687 is open?

On Linux run "ss -ltnup 'sport = :4687'", on macOS "lsof -nP -i :4687", and on Windows "netstat -ano | findstr :4687" to see the local process. From another machine, "nmap -p 4687 <host>" shows whether it is reachable.

05 Related
:445 SMB tcp · udp · critical risk :21 FTP tcp · udp · sctp · high risk :139 NetBIOS Session tcp · udp · high risk :69 TFTP udp · tcp · high risk :2049 NFS tcp · udp · sctp · high risk :873 rsync tcp · udp · high risk :20 File Transfer [Default Data] tcp · udp · sctp :115 Simple File Transfer Protocol tcp · udp

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