Re: Minimum password requirements

[Robert Inder <robert () interactive co uk>]

OK, since this is a security BASICS list, I'm going to risk showing
ignorance and ask some basic quesions:-)

> > > > > Randall M Gunning writes:
    > To: <security-basics () securityfocus com>
    > Subject: Minimum password requirements
    > Date: Thu, 15 Jul 2004 08:26:57 -0700

    > I am working on implementing some minimum standards for our
    > department. I am wondering what the list thinks of these
    > standards:

Obviously, if a password is thought to be compromised, it must
be changed immediately.  

But in the case where is NO reason to suspect compromise...

    > a. Passwords must be changed at least every 90 days.

Why is changing a still-secred password a good thing?

I deal with a number of systems which do this, and even where
I keep a note of the actual password, it is still a MAJOR pain. 

The first time I log in after the enforced password change, I forget
it has happened, have several attempts to use the previous one, and 
the account locks before I realise.  On one system I have a 100%
record of having to phone up and get the account re-enabled (using the
password on the letter they sent me when the account was opened!)

So why do they do this?  What is the threat that is large enough to
justify forcing me to regularly come up with new passwords that must
complex/unmemorable enough to need to be written down?

    > b. Passwords cannot be changed for at least 14 days.

Why is this a good thing?  Is it somethign to do with
letting users "flush" the "queue" of previous passwords?

    > c. Previous passwords cannot be reused (at least the last 10).

Obviously, there is no point in making me change it if I can then just
change it back again....


    > d. User ids and passwords are "owned" by an individual and must not be
    > shared with others.

    > e. User accounts that have not been accessed (i.e. logged in to)
    > for 30 days will be deactivated.

Well, this obviously reduces the number of "targets" (accounts) that a
would-be cracker has to shoot at, and protects this system against
someone who has obtained the user's password for another system.

Is it more than this?  

I can't be alone in having a several accounts that I rarely use
--- either because I need them for infrequent tasks, or because I'm
the "reserve" for doing something.  Either way, the accounts are
seldom used, but de-activating them would have a big impact.  

Is the benefit of so promptly "zapping" dormant accounts enough to
outweigh problems of this type?

    > f. Inactive user accounts will be deleted after 14 days.

Is this more than just general "hygene" and/or tidiness --- 
smaller/simpler/fewer is better?  Or is there a specific risk?

    > The numbers I have used are what I used in the corporate world
    > for systems that had no special security requirements (i.e. they
    > did not have any confidential data on them). What are other
    > people doing for this type of standard, if anything? Also, if
    > you had your choice (not subject to a committee agreeing), what
    > would you choose for these items?

Well, you did say...

    > Please let me know if you have any questions.

    > Thanks,

    > Randy

Robert.

--
Robert Inder      Interactive Information,            07770 30 40 52 (general)
07808 492 213     3, Lauriston Gardens,                    0131 229 1052 (fax)
                  Edinburgh EH3 9HH
                  SCOTLAND UK             Interactions speak louder than words


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