cis-ubuntu1604-v200-5-4-2

name	cis-ubuntu1604-v200-5-4-2
description	Ensure lockout for failed password attempts is configured
category	cis-iam
version	2.0.0
author	cyberstrike-official
tags	["cis","ubuntu","linux","ubuntu-16.04","authentication","pam"]
cis_id	5.4.2
cis_benchmark	CIS Ubuntu Linux 16.04 LTS Benchmark v2.0.0
tech_stack	["ubuntu","linux"]
cwe_ids	[]
chains_with	[]
prerequisites	[]
severity_boost	{}

Ensure lockout for failed password attempts is configured

Profile Applicability:

• Level 1 - Server
• Level 1 - Workstation

Assessment Status: Automated

Description

Lock out users after n unsuccessful consecutive login attempts. The first sets of changes are made to the PAM configuration files. The second set of changes are applied to the program specific PAM configuration file. The second set of changes must be applied to each program that will lock out users. Check the documentation for each secondary program for instructions on how to configure them to work with PAM.

• deny=n - n represents the number of failed attempts before the account is locked
• unlock_time=n - n represents the number of seconds before the account is unlocked
• audit - Will log the user name into the system log if the user is not found.
• silent - Don't print informative messages. Set the lockout number and unlock time in accordance with local site policy.

Rationale

Locking out user IDs after n unsuccessful consecutive login attempts mitigates brute force password attacks against your systems.

Audit Procedure

Command Line

Verify password lockouts are configured. These settings are commonly configured with the pam_tally2.so modules found in /etc/pam.d/common-auth:

grep "pam_tally2" /etc/pam.d/common-auth

Expected output:

auth required pam_tally2.so onerr=fail audit silent deny=5 unlock_time=900

Verify the pam_deny.so module and pam_tally2.so modules are included in /etc/pam.d/common-account:

grep -E "pam_(tally2|deny)\.so" /etc/pam.d/common-account

Expected output:

account requisite                       pam_deny.so
account required                        pam_tally2.so

Remediation

Command Line

Edit the /etc/pam.d/common-auth file and add the auth line below:

auth required pam_tally2.so onerr=fail audit silent deny=5 unlock_time=900