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Dangerous Open Ports


   
   

Port: 21

   

Explanation: This port is used for FTP (File Transfer Protocol).

   

Impact: This port sends its data over plain text, meaning that attackers can abuse this port to intercept and steal credentials.

   

Mitigation: Close port 21.        

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  • Windows: Go to Windows Firewall settings and block port 21.
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  • Linux: Use the command sudo ufw deny 21 to close this port.
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Port: 22

   

Explanation: This port is used for SSH (Secure Shell).

   

Impact: If not properly secured, this port can be exploited by attackers to gain unauthorized access to the system.

   

Mitigation: Secure port 22 by using strong authentication methods, or close it if not in use.        

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  • Windows: Go to Windows Firewall settings and block port 22 if not required.
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  • Linux: Use the command sudo ufw deny 22 to close this port.
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Port: 23

   

Explanation: This port is used for Telnet.

   

Impact: Telnet sends its data, including passwords, over plain text, making it vulnerable to eavesdropping.

   

Mitigation: Close port 23 and use SSH instead.        

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  • Windows: Disable Telnet services and block port 23 in Windows Firewall.
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  • Linux: Use sudo ufw deny 23 to block this port.
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Port: 25

   

Explanation: This port is used for SMTP (Simple Mail Transfer Protocol).

   

Impact: Attackers can exploit this port to send spam or phishing emails if not properly secured.

   

Mitigation: Secure port 25 with proper authentication and spam filtering.        

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  • Windows: Configure mail server settings to require authentication.
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  • Linux: Use firewall rules to restrict access to port 25.
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Port: 53

   

Explanation: This port is used for DNS (Domain Name System).

   

Impact: Open DNS ports can be exploited for DNS amplification attacks.

   

Mitigation: Secure port 53 by configuring DNS servers to prevent open recursion.        

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  • Windows: Configure DNS services to only allow trusted networks.
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  • Linux: Use sudo ufw allow from trusted_ips to any port 53.
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Port: 80

   

Explanation: This port is used for HTTP (Hypertext Transfer Protocol).

   

Impact: HTTP traffic is unencrypted, making it susceptible to eavesdropping and man-in-the-middle attacks.

   

Mitigation: Redirect HTTP traffic to HTTPS (port 443).        

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  • Windows: Configure web server settings to redirect traffic from port 80 to 443.
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  • Linux: Use firewall rules to enforce HTTPS and redirect HTTP traffic.
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