The Ubuntu operating system must automatically lock an account until the locked account is released by an administrator when three unsuccessful logon attempts have been made.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
low	V-238235	SRG-OS-000329-GPOS-00128	UBTU-20-010072	SV-238235r1069092_rule	2025-03-03	2

Description
By limiting the number of failed logon attempts, the risk of unauthorized system access via user password guessing, otherwise known as brute-forcing, is reduced. Limits are imposed by locking the account. Satisfies: SRG-OS-000329-GPOS-00128, SRG-OS-000021-GPOS-00005

ℹ️ Check
Verify the Ubuntu operating system utilizes the "pam_faillock" module with the following command: $ grep faillock /etc/pam.d/common-auth auth [default=die] pam_faillock.so authfail auth sufficient pam_faillock.so authsucc If the pam_faillock.so module is not present in the "/etc/pam.d/common-auth" file, this is a finding. Verify the pam_faillock module is configured to use the following options: $ sudo egrep 'silent\|audit\|deny\|fail_interval\|unlock_time' /etc/security/faillock.conf audit silent deny = 3 fail_interval = 900 unlock_time = 0 If the "silent" keyword is missing or commented out, this is a finding. If the "audit" keyword is missing or commented out, this is a finding. If the "deny" keyword is missing, commented out, or set to a value greater than "3", this is a finding. If the "fail_interval" keyword is missing, commented out, or set to a value greater than "900", this is a finding. If the "unlock_time" keyword is missing, commented out, or not set to "0", this is a finding.

ℹ️ Check

Verify the Ubuntu operating system utilizes the "pam_faillock" module with the following command: $ grep faillock /etc/pam.d/common-auth auth [default=die] pam_faillock.so authfail auth sufficient pam_faillock.so authsucc If the pam_faillock.so module is not present in the "/etc/pam.d/common-auth" file, this is a finding. Verify the pam_faillock module is configured to use the following options: $ sudo egrep 'silent|audit|deny|fail_interval|unlock_time' /etc/security/faillock.conf audit silent deny = 3 fail_interval = 900 unlock_time = 0 If the "silent" keyword is missing or commented out, this is a finding. If the "audit" keyword is missing or commented out, this is a finding. If the "deny" keyword is missing, commented out, or set to a value greater than "3", this is a finding. If the "fail_interval" keyword is missing, commented out, or set to a value greater than "900", this is a finding. If the "unlock_time" keyword is missing, commented out, or not set to "0", this is a finding.

✔️ Fix
Configure the Ubuntu operating system to utilize the "pam_faillock" module. Edit the /etc/pam.d/common-auth file. Add the following lines below the "auth" definition for pam_unix.so: auth [default=die] pam_faillock.so authfail auth sufficient pam_faillock.so authsucc Configure the "pam_faillock" module to use the following options: Edit the /etc/security/faillock.conf file and add/update the following keywords and values: audit silent deny = 3 fail_interval = 900 unlock_time = 0

✔️ Fix

Configure the Ubuntu operating system to utilize the "pam_faillock" module. Edit the /etc/pam.d/common-auth file. Add the following lines below the "auth" definition for pam_unix.so: auth [default=die] pam_faillock.so authfail auth sufficient pam_faillock.so authsucc Configure the "pam_faillock" module to use the following options: Edit the /etc/security/faillock.conf file and add/update the following keywords and values: audit silent deny = 3 fail_interval = 900 unlock_time = 0