CyberHunter
Local dataset, no network
// Other services

Port 3281: SYSOPT

Port 3281 is assigned by IANA to sysopt (SYSOPT).

3281

How sysopt works

Other services
client:3281sysoptresponse client:3281sysoptresponse

The client sends a request to port 3281 and the sysopt 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 3281 dangerous?

We have no specific security note for port 3281. 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 3281

ServicePortTransportDescriptionReferenceUpdated
sysopt 3281 TCP, UDP SYSOPT - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 3281, and is it reachable?

Linux

sudo ss -ltnup 'sport = :3281'      # process listening on 3281
sudo lsof -nP -i :3281

macOS

sudo lsof -nP -i :3281

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 3281 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 3281
netstat -ano | findstr :3281

From another machine

nmap -p 3281 -sV <host>
sudo nmap -sU -p 3281 <host>
nc -zv <host> 3281

Block it in the firewall

sudo ufw deny 3281/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 3281" -Direction Inbound -LocalPort 3281 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 3281 used for?

Port 3281 is assigned by IANA to sysopt (SYSOPT).

Is port 3281 TCP or UDP?

Port 3281 is registered for TCP and UDP.

Is it safe to open port 3281?

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 3281 is open?

On Linux run "ss -ltnup 'sport = :3281'", on macOS "lsof -nP -i :3281", and on Windows "netstat -ano | findstr :3281" to see the local process. From another machine, "nmap -p 3281 <host>" shows whether it is reachable.

05 Related
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