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// Other services

Port 1039: Streamlined Blackhole

Port 1039 is assigned by IANA to sbl (Streamlined Blackhole).

1039

How sbl works

Other services
client:1039sblresponse client:1039sblresponse

The client sends a request to port 1039 and the sbl 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 1039 dangerous?

We have no specific security note for port 1039. 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 1039

ServicePortTransportDescriptionReferenceUpdated
sbl 1039 TCP, UDP Streamlined Blackhole - 2004-11

// source: IANA service name and port number registry

03 Check it

Which program uses port 1039, and is it reachable?

Linux

sudo ss -ltnup 'sport = :1039'      # process listening on 1039
sudo lsof -nP -i :1039

macOS

sudo lsof -nP -i :1039

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 1039 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 1039
netstat -ano | findstr :1039

From another machine

nmap -p 1039 -sV <host>
sudo nmap -sU -p 1039 <host>
nc -zv <host> 1039

Block it in the firewall

sudo ufw deny 1039/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 1039" -Direction Inbound -LocalPort 1039 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 1039 used for?

Port 1039 is assigned by IANA to sbl (Streamlined Blackhole).

Is port 1039 TCP or UDP?

Port 1039 is registered for TCP and UDP.

Is it safe to open port 1039?

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 1039 is open?

On Linux run "ss -ltnup 'sport = :1039'", on macOS "lsof -nP -i :1039", and on Windows "netstat -ano | findstr :1039" to see the local process. From another machine, "nmap -p 1039 <host>" shows whether it is reachable.

05 Related
:4444 Metasploit default / krb524 tcp · udp · high risk :31337 Back Orifice / elite tcp · udp · high risk :1 TCP Port Service Multiplexer tcp · udp :5 Remote Job Entry tcp · udp :9 Discard tcp · udp · sctp · dccp :11 Active Users tcp · udp :17 Quote of the Day tcp · udp :18 Message Send Protocol (historic) tcp · udp

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