Title

IBM z/VM must require the change of at least 50% of the total number of characters when passwords are changed. (Cat II impact)

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 8 characters.

Check Content

If there is no VM:Secure PASSWORD user exit in use, this is a finding. Review the VM:Secure PASSWORD user exit. If there is no code that enforces change of at least 50% of the total number of characters when passwords are changed, this is a finding.

Fix Text

Configure a VM:Secure PASSWORD user exit that enforces change of at least 50% of the total number of characters when passwords are changed. Ensure that the following Macros are updated with proper PASSWORD user exit: FORCEPWC VMXCHGPW MAINT USE00080

Additional Identifiers

Rule ID:

Vulnerability ID: IBMZ-VM-000400

Group Title:

Expert Comments

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