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V-223504

CAT II (Medium)

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

Rule ID

SV-223504r1001111_rule

STIG

IBM z/OS ACF2 Security Technical Implementation Guide

Version

V9R8

CCIs

CCI-004065 CCI-004066

Discussion

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 eight characters.

Check Content

From an ACF command screen enter:
SET CONTROL(GSO)
LIST PSWD

If "PSWDSIM" is set to "4", this is not a finding.

Fix Text

Configure the Password option "PSWDSIM" to "4".