Password policies in AD

One of the more annoying problems with password and account-lockout policies in Active Directory has been that they apply to every account universally. I you want to force your users to change passwords every 90 days, with account lockout after a certain number of bad login attempts, then the same policies apply to your 'Administrator' user. Account lock-out was a really great way to DoS yourself in really critical ways.

In a way, that's what account-lockout is all about. It's to keep bad people from coming in, but its also a way for bad people from preventing legitimate people from using their own accounts. You need to take the good with the bad.

Since we were a NetWare shot for y-e-a-r-s we're very used to Intruder Lockout (ILO), and losing it during the move to Windows was seen as a loss of a key security feature. We had accounts that had to be exempted from lockout, which was dead easy in eDirectory but very difficult in AD.

Happily, Server 2008 introduces a way to do this. It's called "Fine-Grained Password Policy", and is NOT group-policy based. This was somewhat surprising. Getting this requires raising the domain and forest functional levels to the 2008 level. What it allows is setting password policy based on group memberships, with conflict resolution handled by a priority setting on the policy itself. Interestingly, the actual policies are created through ASDI Edit, so they're not beginner-friendly.

For instance, we can set a 'lock out after 6 tries in 30 minutes' setting to the Domain Users group at a Priority of 30, and a second 'never lock out ever' policy to the Domain Admins group at a Priority of 20. That way 'Administrator' will have the never-lock policy apply to it, but Joe User will have the lock-after-6-in-30 policy apply. This works best if the password policy specifies that Domain Admins need to have very complex and long passwords, which makes a brute-force cracking attempt take unreasonably long amounts of time.

We put this in place a few weeks ago, and it is working as we expected. SO GLAD to have this.