Cis Ubuntu1804 V220 1 7 2

1.7.2 Ensure local login warning banner is configured properly (Automated)

Profile Applicability

• Level 1 - Server
• Level 1 - Workstation

Description

The contents of the /etc/issue file are displayed to users prior to login for local terminals.

Unix-based systems have typically displayed information about the OS release and patch level upon logging in to the system. This information can be useful to developers who are developing software for a particular OS platform. If mingetty(8) supports the following options, they display operating system information: \m - machine architecture \r - operating system release \s - operating system name \v - operating system version - or the operating system's name

Rationale

Warning messages inform users who are attempting to login to the system of their legal status regarding the system and must include the name of the organization that owns the system and any monitoring policies that are in place. Displaying OS and patch level information in login banners also has the side effect of providing detailed system information to attackers attempting to target specific exploits of a system. Authorized users can easily get this information by running the uname -a command once they have logged in.

Audit Procedure

Command Line

Run the following command and verify that the contents match site policy:

cat /etc/issue

Run the following command and verify no results are returned:

grep -E -i "(\\v|\\r|\\m|\\s|$(grep '^ID=' /etc/os-release | cut -d= -f2 | sed -e 's/"//g'))" /etc/issue

Expected Result

Nothing should be returned from the grep command.

Remediation

Command Line

Edit the /etc/issue file with the appropriate contents according to your site policy, remove any instances of \m, \r, \s, \v or references to the OS platform. Add or update the message text to follow local site policy.

Example Text:

echo "Authorized use only. All activity may be monitored and reported." > /etc/issue

References

1. NIST SP 800-53 Rev. 5: CM-6, CM-1, CM-3

MITRE ATT&CK Mappings