Details

Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks. If the information system or application allows the user to consecutively reuse their password when that password has exceeded its defined lifetime, the end result is a password that is not changed as per policy requirements.

Solution

Configure the Ubuntu operating system prevents passwords from being reused for a minimum of five generations.

Add or modify the ‘remember’ parameter value to the following line in ‘/etc/pam.d/common-password’ file:

password [success=1 default=ignore] pam_unix.so obscure sha512 remember=5 rounds=5000

Supportive Information

The following resource is also helpful.

• https://dl.dod.cyber.mil/wp-content/uploads/stigs/zip/U_CAN_Ubuntu_16-04_LTS_V2R3_STIG.zip

This security hardening control applies to the following category of controls within NIST 800-53: Identification and Authentication.This control applies to the following type of system Unix.

References

• 800-53|IA-5(1)(e)
• CAT|II
• CCI|CCI-000200
• Rule-ID|SV-214961r610931_rule
• STIG-ID|UBTU-16-010230
• STIG-Legacy|SV-90155
• STIG-Legacy|V-75475
• Vuln-ID|V-214961

Source

• Tenable.com/audits