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// Other services

Port 3761: gsakmp port

Port 3761 is assigned by IANA to gsakmp (gsakmp port).

3761

How gsakmp works

Other services
client:3761gsakmpresponse client:3761gsakmpresponse

The client sends a request to port 3761 and the gsakmp service answers.

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
Other services
01 Security

Is port 3761 dangerous?

We have no specific security note for port 3761. 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 3761

ServicePortTransportDescriptionReferenceUpdated
gsakmp 3761 TCP, UDP gsakmp port RFC 4535 -

// source: IANA service name and port number registry

03 Check it

Which program uses port 3761, and is it reachable?

Linux

sudo ss -ltnup 'sport = :3761'      # process listening on 3761
sudo lsof -nP -i :3761

macOS

sudo lsof -nP -i :3761

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 3761 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 3761
netstat -ano | findstr :3761

From another machine

nmap -p 3761 -sV <host>
sudo nmap -sU -p 3761 <host>
nc -zv <host> 3761

Block it in the firewall

sudo ufw deny 3761/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 3761" -Direction Inbound -LocalPort 3761 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 3761 used for?

Port 3761 is assigned by IANA to gsakmp (gsakmp port).

Is port 3761 TCP or UDP?

Port 3761 is registered for TCP and UDP.

Is it safe to open port 3761?

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 3761 is open?

On Linux run "ss -ltnup 'sport = :3761'", on macOS "lsof -nP -i :3761", and on Windows "netstat -ano | findstr :3761" to see the local process. From another machine, "nmap -p 3761 <host>" shows whether it is reachable.

05 Related
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