Re: concurrent logins

[Seth Art <sethsec () gmail com>]

As a user, I love how gmail does it, and I would love to see that more.

As a tester, I personally treat this one as more of a recommendation
than a finding in most cases.  I find this one is difficult to defend
in findings review meetings, especially given the challenges you
mention, and the pervasiveness of popular applications on the internet
that allow concurrent logins.

I think you covered the ways to handle this very well.  I think it
just depends on the level of security you want to achieve.  I guess a
slightly modified option would be to add some logic similar to what
some of the 2FA solutions do now:  You could require an extra step if
the IP (or a combination of characteristics) of the second session has
not been seen before.

On Wed, Nov 19, 2014 at 5:30 AM, Robin Wood <robin@digi.ninja> wrote:
> What are peoples opinions on allowing concurrent logins to web apps? I
> suppose it depends on what the app is used for - forum, admin suite
> etc - but do the protections from it add more problems that allowing
> it?
>
> Solutions I can see are:
>
> 1. Allow concurrent logins
> 2. Allow concurrent logins but report that someone else is logged it -
> like Gmail does
> 3. Don't allow them and kick out any logged in user when a new one logs in
> 4. Don't allow them and lock out all new logins till old ones have logged out
> 5. Give a warning popup when logging in to say the account is in use
> elsewhere as well
> 6. Allow but report back to an admin or log tracker or similar
>
> 1 is the default in most cases.
> 2 is a good idea but really, how many people look at the little thing
> in Gmail which says where else the account is logged in from, I don't
> and I'm sure normal users don't even know it exists.
> 3. Good but if an attacker gets creds or a reliable session hijack
> then they can use them to DoS legit users by keep logging them out.
> 4. Good but if an attacker gets in they can keep the account active
> and so DoS the real user by never letting them log in.
> 5. Maybe the best option but only works in the legit user logs in
> second otherwise the attacker gets the warning and ignores it.
> 6. Good one if people are watching the logs and can act on them.
>
> What other options are there? Can it be done in a good way that makes
> if of any use?
>
> Robin
>
>
>
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