I agree that scripted attacks (which aren't mitigated by password changes) dominate, and targeted attacks are less common. Nevertheless, the latter do occur. As for brute-force attacks... Cryptography isn't my specialty, but I think you may be underestimating the time it takes to crack a complex password/passphrase.
Changing passwords is a nominal task. It takes maybe 60 seconds to do. The real loss of productivity and introduction of new risk come from forgetting the new password or writing it down and storing it in an obvious location-both of which are behaviors that can easily be changed with a bit of training. John From: Andrew S. Baker [mailto:asbz...@gmail.com] Sent: Friday, April 16, 2010 10:14 AM To: NT System Admin Issues Subject: Re: please don't change your password! This fails to consider the situation where a user's password is compromised and the bad guy accesses the user's information on an ongoing basis. For instance, monitoring a folder that contains files with information about patent filings to see when new files show up, or logging into OWA to keep an eye on e-mail messages. The unauthorized access will end once the password is changed (assuming a variety of other factors, such as the bad guy not getting the new password, etc.), and thus requiring regular password changes can be of value. We live in a world where scripted attacks dominate, and where targeted attacks are against highly privileged assets. Add to that, most scripted attacks are aimed at an application or OS or protocol vulnerability, with the primary intent of sending spam or rooting the machine in some way. Thus, the changing of passwords does little to mitigate any of the aforementioned. Even a targeted attack is likely to take steps to elevate privileges and creating a new account for the purpose of removing reliance on the compromised account. Similarly, regular password changes can mitigate the risk from brute-force attacks. If a password has to be changed every 60 days, for instance, the bad guy will only have 60 days to try to determine the user's password. This is generally considered to be better than the bad guy having an infinite amount of time to try to determine it. In most cases, it doesn't take weeks to brute force an account. Mostly hours, and occasionally days. (Doesn't everyone have a quad-core system or set of systems?) But that's not really the point. Most breaches today aren't accomplished via brute force of the password. There are hundreds of other approaches to get into systems remote that require far less time and effort, and all lead to elevated rights. -ASB: http://XeeSM.com/AndrewBaker On Fri, Apr 16, 2010 at 8:51 AM, John Hornbuckle <john.hornbuc...@taylor.k12.fl.us<mailto:john.hornbuc...@taylor.k12.fl.us>> wrote: There's a flaw in the logic. The Globe article states: " . . . [U]sers are admonished to change passwords regularly, but redoing them is not an effective preventive step against online infiltration unless the cyber attacker (or evil colleague) who steals your sign-in sequence waits to employ it until after you've switched to a new one, Herley wrote. That's about as likely as a crook lifting a house key and then waiting until the lock is changed before sticking it in the door." This fails to consider the situation where a user's password is compromised and the bad guy accesses the user's information on an ongoing basis. For instance, monitoring a folder that contains files with information about patent filings to see when new files show up, or logging into OWA to keep an eye on e-mail messages. The unauthorized access will end once the password is changed (assuming a variety of other factors, such as the bad guy not getting the new password, etc.), and thus requiring regular password changes can be of value. Similarly, regular password changes can mitigate the risk from brute-force attacks. If a password has to be changed every 60 days, for instance, the bad guy will only have 60 days to try to determine the user's password. This is generally considered to be better than the bad guy having an infinite amount of time to try to determine it. John Hornbuckle MIS Department Taylor County School District www.taylor.k12.fl.us<http://www.taylor.k12.fl.us> From: Brian Clark [mailto:brianclark2...@googlemail.com<mailto:brianclark2...@googlemail.com>] Sent: Thursday, April 15, 2010 4:38 PM To: NT System Admin Issues Subject: please don't change your password! After a long week doing a SBS migration I didn't know how to take this article and needed to share it!! http://www.boston.com/bostonglobe/ideas/articles/2010/04/11/please_do_not_change_your_password/?page=1 Brian NOTICE: Florida has a broad public records law. Most written communications to or from this entity are public records that will be disclosed to the public and the media upon request. E-mail communications may be subject to public disclosure. ~ Finally, powerful endpoint security that ISN'T a resource hog! ~ ~ <http://www.sunbeltsoftware.com/Business/VIPRE-Enterprise/> ~
