Title

The operating system must require the change of at least 50 percent 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 eight characters.

Check Content

Verify the operating system requires the change of at least eight of the total number of characters when passwords are changed. If it does not, this is a finding.

Fix Text

Configure the operating system to require the change of at least eight of the total number of characters when passwords are changed.

Additional Identifiers

Rule ID: SV-203628r982198_rule

Vulnerability ID: V-203628

Group Title: SRG-OS-000072

Expert Comments

CCIs tied to check.

Controls tied to check. These are derived from the CCIs shown above.