cyberstrikeus Ensure telnet client is not installed
Profile
- Level 1 - Server
- Level 1 - Workstation
Description
The telnet package contains the telnet client, which allows users to start connections to other systems via the telnet protocol.
Rationale
The telnet protocol is insecure and unencrypted. The use of an unencrypted transmission medium could allow an unauthorized user to steal credentials. The ssh package provides an encrypted session and stronger security and is included in most Linux distributions.
Impact
Many insecure service clients are used as troubleshooting tools and in testing environments. Uninstalling them can inhibit capability to test and troubleshoot. If they are required it is advisable to remove the clients after use to prevent accidental or intentional misuse.
Audit
Verify telnet is not installed. Use the following command to provide the needed information:
Command Line
# dpkg-query -s telnet &>/dev/null && echo "telnet is installed"
Expected Result
Nothing should be returned.
Remediation
Uninstall telnet:
Command Line
# apt purge telnet
References
- NIST SP 800-53 Rev. 5: CM-7, CM-11
CIS Controls
| Controls Version | Control | IG 1 | IG 2 | IG 3 |
|---|---|---|---|---|
| v8 | 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and SoftwareUninstall or disable unnecessary services on enterprise assets and software, such as an unused file sharing service, web application module, or service function. | ● | ● | |
| v7 | 9.2 Ensure Only Approved Ports, Protocols and Services Are RunningEnsure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. | ● | ● |
MITRE ATT&CK Mappings
| Techniques / Sub-techniques | Tactics | Mitigations |
|---|---|---|
| T1040, T1040.000, T1203, T1203.000, T1543, T1543.002 | TA0006, TA0008 | M1041, M1042 |