Vulnerability Discussion

The Ubuntu operating system management includes the ability to control the number of users and user sessions that utilize an operating system. Limiting the number of allowed users and sessions per user is helpful in reducing the risks related to DoS attacks.

This requirement addresses concurrent sessions for information system accounts and does not address concurrent sessions by single users via multiple system accounts. The maximum number of concurrent sessions should be defined based upon mission needs and the operational environment for each system.

Check

Verify the Ubuntu operating system limits the number of concurrent sessions to 10 for all accounts and/or account types by running the following command:

$ grep maxlogins /etc/security/limits.conf | grep -v '^* hard maxlogins'

The result must contain the following line:

* hard maxlogins 10

If the "maxlogins" item is missing or the value is not set to 10 or less or is commented out, this is a finding.

Fix

Configure the Ubuntu operating system to limit the number of concurrent sessions to 10 for all accounts and/or account types.

Add the following line to the top of the "/etc/security/limits.conf" file:

* hard maxlogins 10