Re: concurrent logins

[Irene Abezgauz <irene.abezgauz () gmail com>]

Hi,

some thoughts, no particular order.

People use multiple devices, so disallowing concurrent logins is not an
option for most sites.

This obviously depends on functionality. Social communication sites do not
have the same needs as banking apps or nuclear-launch-management-interface
etc.


looking at your 1-6:
1. Allow concurrent logins <-- most sites
2. Allow concurrent logins but report that someone else is logged it -
like Gmail does <-- many sites. this is not bad especially the google way
such as putting a bigger, more noticeable line if they see a specific
problem (for example deviation from behavioral patterns)
3. Don't allow them and kick out any logged in user when a new one logs in
<-- few sites. often thick clients etc. In many cases this is due to
application functionality more than security needs ;)
4. Don't allow them and lock out all new logins till old ones have logged
out <-- that can cause functionality problems, such as the admin that
locked a bunch of files and interfaces and then went on vacation.
5. Give a warning popup when logging in to say the account is in use
elsewhere as well <-- I like this one, but it's not a one-size-fits-all
solution. nobody wants this annoyance on their social network site.
6. Allow but report back to an admin or log tracker or similar <-- depends
on the site. on large traffic sites you can't really have multiple logins
reporting to admin.


if to break this into a very rough site-type classification:

1. Retail - no reason not to allow multiple connections. users want to be
able to log in from their tablet, but also from their phone and/or laptop.
You can require additional authentication (password for example) before
important operations. Concurrency - not necessarily a problem.
2. Banking/similar - Although you don't really have to allow concurrent
connections, most sites won't block it. Again, you need to look at the
risk. A lot of the controls are done on different levels - such as
monitoring the standard 'behavior' patterns of a user and then checking
whether the new login matches that and if needed utilizing a secondary
security mechanism
3. Social sites (FB, linkedin, or
whatever-young-people-are-using-these-days) - again - concurrent logins are
usually needed. FB and similar send you an email saying 'new device' and
you can also configure to disable.
4. sensitive interfaces - usually not a lot of users. be the annoying
security person and play with settings as much as you want :)


the bigger question here is - what are you trying to achieve?

disabling concurrent logins because security? I'm not sure that's the way
to go for most apps. notifying the user - yes you can do that, most of them
won't know what to do with it.

2FA (not bullet proof, but efficient in most scenarios these days),
notifications of new device, extra security layer if behavior is
non-standard (different country in a short time, etc) is probably better
than just 'don't do concurrent logins'.

Irene

On Wed, Nov 19, 2014 at 12:30 PM, 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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