Vulnerability Discussion

Without protection of the transmitted information, confidentiality and integrity may be compromised because unprotected communications can be intercepted and either read or altered.

This requirement applies to both internal and external networks and all types of information system components from which information can be transmitted (e.g., servers, mobile devices, notebook computers, printers, copiers, scanners, and facsimile machines). Communication paths outside the physical protection of a controlled boundary are exposed to the possibility of interception and modification.

Protecting the confidentiality and integrity of organizational information can be accomplished by physical means (e.g., employing physical distribution systems) or by logical means (e.g., employing cryptographic techniques). If physical means of protection are employed, then logical means (cryptography) do not have to be employed, and vice versa.

Alternative physical protection measures include PDS. PDSs are used to transmit unencrypted classified National Security Information (NSI) through an area of lesser classification or control. Since the classified NSI is unencrypted, the PDS must provide adequate electrical, electromagnetic, and physical safeguards to deter exploitation.

Satisfies: SRG-OS-000423-GPOS-00187, SRG-OS-000424-GPOS-00188, SRG-OS-000425-GPOS-00189, SRG-OS-000426-GPOS-00190

Check

Check that the ssh package is installed with the following command:

# sudo dpkg -l | grep openssh
ii openssh-client 1:7.6p1-4ubuntu0.1 amd64 secure shell (SSH) client, for secure access to remote machines
ii openssh-server 1:7.6p1-4ubuntu0.1 amd64 secure shell (SSH) server, for secure access from remote machines
ii openssh-sftp-server 1:7.6p1-4ubuntu0.1 amd64 secure shell (SSH) sftp server module, for SFTP access from remote machines

If the "openssh" server package is not installed, this is a finding.

Check that the "sshd.service" is loaded and active with the following command:

# sudo systemctl status sshd.service | egrep -i "(active|loaded)"
Loaded: loaded (/lib/systemd/system/ssh.service; enabled; vendor preset: enabled)
Active: active (running) since Thu 2019-01-24 22:52:58 UTC; 1 weeks 3 days ago

If "sshd.service" is not active or loaded, this is a finding.

Fix

Install the "ssh" meta-package on the system with the following command:

# sudo apt install ssh

Enable the "ssh" service to start automatically on reboot with the following command:

# sudo systemctl enable sshd.service

Ensure that the "ssh" service is running.

# sudo systemctl start sshd.service