Re: account enumeration

[Zate <zate75 () gmail com>]

> If you dropped the random four digits would you get problems with
> impersonation  where one Bugsbunny could pretend to be another once in
> the system?

Yeah you need the 4 digits to maintain uniqueness of the persona.  You
could represent them without it on the UI such as "Welcome back Bugsbunny"
instead of "Welcome back Bugsbunny.7854" but you need to maintain
uniqueness for the item you are using for Auth and I'd prefer in my system
to use persona rather than email address.  Never have to change persona,
but you might need to change email address.


> Someone on Twitter pointed out that maybe the user names should not be
> private and I've been thinking about that. If you have good
> protections in place to prevent things like password brute force what
> is the issue with attackers finding the names of system users. If the
> system is implemented like you suggest and personas are used rather
> than email addresses then if someone wants to stay anonymous they just
> avoid re-use of a persona across multiple systems. I have a feeling
> that this is wrong but can't put my finger on why.
Persona/username wouldn't be private.  if it was a forum, it's be right
beside the post you made etc.  The other bonus to using 4 digits is
uniqueness per ecosystem.  If Game/App A where I am SnowWhite gets popped,
we often see the bad guys try Game/App B with SnowWhite and the same
password.  If i am SnowWhite.2190 on game A and SnowWhite.2345 on B, the
bad guys have no real way to know that from the dump they got from Game A's
poorly secured forums. Yeah I need to remember my username on 2 systems but
I can always recover if need be.

And yes, you can use diff personas across duff systems entirely, allowing
you to be anonymous on the new system even while keeping the same email
address.

I've seen instances where Place X gets compromised, and immediately 24
hours later our brute force alarms would go off as the email/pass list from
Place X was ran over our system.  We had a lot of other systems in place
(such as some amazing in app logging, machine/browser finger printing and
Splunk, wonderful awesome never leave home without it Splunk) and we were
able to find compromised accounts in minutes and reset the password almost
on an automated basis.  Had to piss off some of the bad guys for sure.




> That sounds like a good idea. Assume they attempt to log in and after
> successful authentication they are securely sent a OTP which then lets
> them finish authentication. If the OTP is used before successful
> authentication then an attacker could flood a valid user with OTPs.


Correct.  The OTP was used after a successful auth from a system not in the
whitelist.  Lots of sites do it today, Steam is a good example. Code gets
sent to your email address (and as such you are trusting the user owns
their email account, if they dont, well they probably have a host of other
problems) and then you enter it.

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