Ensure there is no unrestricted inbound access to TCP port 23 (Telnet)

Security & Compliance

Telnet is an unencrypted protocol that enables users to connect to a remote server or device and execute commands as if they were physically present at the console. However, because Telnet transmits data in plain text, it is vulnerable to eavesdropping and interception attacks. Therefore, it is important to ensure that there is no unrestricted inbound access to TCP port 23 (Telnet) to reduce the risk of unauthorized access and data breaches.


Telnet is an insecure protocol that transmits login credentials in plaintext, making it vulnerable to eavesdropping attacks. Therefore, it is recommended to restrict the inbound access to TCP port 23 to prevent unauthorized access to Telnet services.

To remediate this issue, follow these steps:

  1. Identify the security group(s) associated with the affected EC2 instance(s) or VPC(s) using Telnet on TCP port 23.
  2. Modify the security group(s) to remove the inbound rule(s) allowing unrestricted access to TCP port 23.
  3. If Telnet is needed for specific purposes, use SSH or a VPN connection as a secure alternative to Telnet.
  4. Monitor the security group(s) periodically to ensure that no new inbound rules are added to TCP port 23 without proper justification.

By following these remediation steps, you can ensure that your network is protected against potential Telnet-related security threats.

Enforced Resources
Note: Remediation steps provided by Lightlytics are meant to be suggestions and guidelines only. It is crucial to thoroughly verify and test any remediation steps before applying them to production environments. Each organization's infrastructure and security needs may differ, and blindly applying suggested remediation steps without proper testing could potentially cause unforeseen issues or vulnerabilities. Therefore, it is strongly recommended that you validate and customize any remediation steps to meet your organization's specific requirements and ensure that they align with your security policies and best practices.