ACF2 PSWD GSO record value must be set to require the change of at least 50% of the total number of characters when passwords are changed.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-223504	ACF2-ES-000870	SV-223504r695433_rule		Medium

Description
If the operating system allows the user to consecutively reuse extensive portions of passwords, this increases the chances of password compromise by increasing the window of opportunity for attempts at guessing and brute-force attacks. The number of changed characters refers to the number of changes required with respect to the total number of positions in the current password. In other words, characters may be the same within the two passwords; however, the positions of the like characters must be different. If the password length is an odd number then number of changed characters must be rounded up. For example, a password length of 15 characters must require the change of at least 8 characters.

Description

If the operating system allows the user to consecutively reuse extensive portions of passwords, this increases the chances of password compromise by increasing the window of opportunity for attempts at guessing and brute-force attacks. The number of changed characters refers to the number of changes required with respect to the total number of positions in the current password. In other words, characters may be the same within the two passwords; however, the positions of the like characters must be different. If the password length is an odd number then number of changed characters must be rounded up. For example, a password length of 15 characters must require the change of at least 8 characters.

STIG	Date
IBM z/OS ACF2 Security Technical Implementation Guide	2022-12-14

Details

Check Text ( C-25177r695432_chk )
From an ACF command screen enter: SET CONTROL(GSO) LIST PSWD If "PSWDSIM" is set to "4", this is not a finding.

Fix Text (F-25165r500646_fix)
Configure the Password option "PSWDSIM" to "4".