AD and enforced password policies

Måns Nilsson mansaxel at
Tue Jan 3 08:44:11 UTC 2012

Subject: RE: AD and enforced password policies Date: Mon, Jan 02, 2012 at 11:15:08PM +0000 Quoting Blake T. Pfankuch (blake at

> However I would say 365 day expiration is a little long, 3 months is about the average in a non financial oriented network.  

If you force me to change a password every three months, I'm going
to start doing "g0ddw/\ssPOrd-01", ..-02, etc immediately. Net result,
you lose.

Let's face it, either the bad guys have LANMAN hashes/unsalted MD5 etc,
and we're all doomed, or they will be lucky and guess. None of these
attack modes will be mitigated by the 3-month scheme; success/fail as
seen by the bad guys will be a lot quicker than three months. If they
do not get lucky with john or rainbow tables, they'll move on.

(Some scenarios still are affected by this, of course, but there is a
lot to be done to stop bad things from happening like not getting your
hashes stolen etc. On-line repeated login failures aren't going to work
because you'll detect that, right? )

Either way, expiring often is the first and most effective step at making
the lusers hate you and will only bring the Post-It(tm) makers happy.

If your password crypto is NSA KW-26 or similar, OTOH, just
don the Navy blues and start swapping punchcards at 0000 ZULU.

Måns Nilsson     primary/secondary/besserwisser/machina
MN-1334-RIPE                             +46 705 989668
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