RHEL 9 must require the change of at least four character classes when passwords are changed.

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.

Password complexity is one factor of several that determines how long it takes to crack a password. The more complex a password, the greater the number of possible combinations that need to be tested before the password is compromised.

Verify that RHEL 9 requires passwords to contain at least four character classes.

$ grep minclass /etc/security/pwquality.conf /etc/security/pwquality.conf.d/*.conf

minclass = 4

If the value of "minclass" is set to less than "4", or is commented out, this is a finding.

Configure RHEL 9 to require the change of at least four character classes when passwords are changed by setting the "minclass" option.

Add or update the following line in the "/etc/security/pwquality.conf" file or a configuration file in the "/etc/security/pwquality.conf.d/" directory to contain the "minclass" parameter:

minclass = 4