An “open port” is an access point on a computer or server that is reachable and active for traffic. Programs and services communicate with each other via ports – so they are necessary, but also potential vulnerabilities.
A port works like a door: If it is open, data traffic can be allowed through – for example, to access websites (port 80/443) or remote maintenance (port 22 for SSH). An “open” port means that this service is reachable and accepts connections.
Open ports are needed so that:
websites are accessible
Email communication works
Remote access (e.g. remote maintenance or VPN) is possible
Servers can communicate with clients
IT service providers open ports, e.g. to set up remote access to a system
Web servers or mail servers in the company need certain open ports to be reachable
Firewall configurations need to decide which ports are open or closed
Vulnerability scans or pentests regularly reveal insecure open ports
Cyberattacks (e.g. ransomware) often use outdated or unnecessarily opened ports as a gateway
Leave only necessary ports open
Consistently close all ports that are not absolutely necessary for operation. Every unnecessary “open gate” increases the risk.
Configure your firewall consistently
Use a central firewall (e.g. in the router or the UTM solution) to allow or block access in a targeted manner. Windows/Linux firewalls should also be enabled.
Restrict access (e.g., IP-based)
Restrict remote access to specific IP addresses or countries. This prevents everyone worldwide from accessing open services.
VPN instead of direct port sharing
If possible, avoid direct sharing of sensitive services such as Remote Desktop (RDP) or SSH. Instead, use a secured VPN to allow remote access.
Keep services up-to-date
Ensure regular updates of the systems and services running behind the ports. Outdated software is often vulnerable.
Perform port scans (have them performed)
Perform regular port scans (e.g. with the help of an IT service provider) to detect unintentionally opened ports at an early stage.
Set up monitoring
Monitor activity on open ports – e.g. through an intrusion detection system (IDS) or log evaluation. In this way, attacks or abuse can be detected at an early stage.
