CyberHunter
Local dataset, no network
// Other services

Port 3773: ctdhercules

Port 3773 is assigned by IANA to ctdhercules (ctdhercules).

3773

How ctdhercules works

Other services
client:3773ctdherculesresponse client:3773ctdherculesresponse

The client sends a request to port 3773 and the ctdhercules 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 3773 dangerous?

We have no specific security note for port 3773. 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 3773

ServicePortTransportDescriptionReferenceUpdated
ctdhercules 3773 TCP, UDP ctdhercules - 2003-06

// source: IANA service name and port number registry

03 Check it

Which program uses port 3773, and is it reachable?

Linux

sudo ss -ltnup 'sport = :3773'      # process listening on 3773
sudo lsof -nP -i :3773

macOS

sudo lsof -nP -i :3773

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 3773 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 3773
netstat -ano | findstr :3773

From another machine

nmap -p 3773 -sV <host>
sudo nmap -sU -p 3773 <host>
nc -zv <host> 3773

Block it in the firewall

sudo ufw deny 3773/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 3773" -Direction Inbound -LocalPort 3773 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 3773 used for?

Port 3773 is assigned by IANA to ctdhercules (ctdhercules).

Is port 3773 TCP or UDP?

Port 3773 is registered for TCP and UDP.

Is it safe to open port 3773?

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 3773 is open?

On Linux run "ss -ltnup 'sport = :3773'", on macOS "lsof -nP -i :3773", and on Windows "netstat -ano | findstr :3773" to see the local process. From another machine, "nmap -p 3773 <host>" shows whether it is reachable.

05 Related
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