{"id":26702,"date":"2022-04-22T11:53:00","date_gmt":"2022-04-22T09:53:00","guid":{"rendered":"https:\/\/perseus.de\/open-ports\/"},"modified":"2026-03-30T10:57:13","modified_gmt":"2026-03-30T08:57:13","slug":"open-ports","status":"publish","type":"post","link":"https:\/\/perseus.de\/en\/open-ports\/","title":{"rendered":"Open Ports"},"content":{"rendered":"\t\t
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Open Ports\n<\/h1>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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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 \u2013 so they are necessary, but also potential vulnerabilities. <\/p>

<\/h4>

What does that mean in detail?<\/strong><\/h4>

A port works like a door: If it is open, data traffic can be allowed through \u2013 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. <\/p>

<\/h4>

Why do you need open ports?<\/strong><\/h4>

Open ports are needed so that:<\/p>

  • websites are accessible<\/p><\/li>

  • Email communication works<\/p><\/li>

  • Remote access (e.g. remote maintenance or VPN) is possible<\/p><\/li>

  • Servers can communicate with clients<\/p><\/li><\/ul>

    <\/h4>

    Where do I encounter this topic in the everyday work of an SME?<\/strong><\/h4>

    • IT service providers open ports<\/strong>, e.g. to set up remote access to a system<\/p><\/li>

    • Web servers or mail servers<\/strong> in the company need certain open ports to be reachable<\/p><\/li>

    • Firewall configurations<\/strong> need to decide which ports are open or closed<\/p><\/li>

    • Vulnerability scans or pentests<\/strong> regularly reveal insecure open ports<\/p><\/li>

    • Cyberattacks<\/strong> (e.g. ransomware) often use outdated or unnecessarily opened ports as a gateway<\/p><\/li><\/ul>

      <\/h4>

      Protection against cyberattacks via open ports<\/strong><\/h4>

      1. Leave only necessary ports open<\/strong>
        Consistently close all ports that are not absolutely necessary for operation. Every unnecessary “open gate” increases the risk. <\/p><\/li>

      2. Configure your firewall consistently<\/strong>
        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. <\/p><\/li>

      3. Restrict access (e.g., IP-based)<\/strong>
        Restrict remote access to specific IP addresses or countries. This prevents everyone worldwide from accessing open services. <\/p><\/li>

      4. VPN instead of direct port sharing<\/strong>
        If possible, avoid direct sharing of sensitive services such as Remote Desktop (RDP) or SSH. Instead, use a secured VPN to allow remote access. <\/p><\/li>

      5. Keep services up-to-date<\/strong>
        Ensure regular updates of the systems and services running behind the ports. Outdated software is often vulnerable. <\/p><\/li>

      6. Perform port scans (have them performed)<\/strong>
        Perform regular port scans (e.g. with the help of an IT service provider) to detect unintentionally opened ports at an early stage.<\/p><\/li>

      7. Set up monitoring<\/strong>
        Monitor activity on open ports \u2013 e.g. through an intrusion detection system (IDS) or log evaluation. In this way, attacks or abuse can be detected at an early stage.<\/p><\/li><\/ol><\/div><\/div><\/div><\/div><\/div><\/div><\/div><\/div><\/div><\/div><\/div><\/div><\/div><\/header>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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        Open Ports 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 \u2013 so they are necessary, but also potential vulnerabilities. What does that mean in detail? 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Programs and services communicate with each other via ports \u2013 so they are necessary, but also potential vulnerabilities. What does that mean in detail? 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