The Ubuntu operating system must be configured so that when passwords are changed or new passwords are established, pwquality must be used.

Use of a complex password helps to increase the time and resources required to compromise the password. Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks. "pwquality" enforces complex password construction configuration and has the ability to limit brute-force attacks on the system.

Verify the Ubuntu operating system has the "libpam-pwquality" package installed by running the following command:

$ dpkg -l libpam-pwquality 

ii libpam-pwquality:amd64 1.4.0-2 amd64 PAM module to check password strength

If "libpam-pwquality" is not installed, this is a finding.

Verify that the operating system uses "pwquality" to enforce the password complexity rules.

Verify the pwquality module is being enforced by the Ubuntu operating system by running the following command:

$ grep -i enforcing /etc/security/pwquality.conf 

enforcing = 1

If the value of "enforcing" is not "1" or the line is commented out, this is a finding.

Check for the use of "pwquality" with the following command:

$ cat /etc/pam.d/common-password | grep requisite | grep pam_pwquality 

password requisite pam_pwquality.so retry=3

If no output is returned or the line is commented out, this is a finding.

If the value of "retry" is set to "0" or greater than "3", this is a finding.

Configure the operating system to use "pwquality" to enforce password complexity rules.

Install the "pam_pwquality" package by using the following command:

$ sudo apt-get install libpam-pwquality -y 

Add the following line to "/etc/security/pwquality.conf" (or modify the line to have the required value):

enforcing = 1

Add the following line to "/etc/pam.d/common-password" (or modify the line to have the required value):

password requisite pam_pwquality.so retry=3

Note: The value of "retry" should be between "1" and "3".