Sunday, July 3, 2011

Account security when visiting other peoples’ computers and the additional danger of federated authentication - use Incognito!

You know when you need to access your email or a document or look up information on a CRM but you are not on your computer? Perhaps it’s a colleague's or a customer's PC. Have you ever considered that you may be leaving passwords or cookies which would allow them access to your personal or company secrets on that computer? Often closing the web browser’s window or clicking ‘Do not remember password’ is not enough - there could easily be authentication cookies left around. You might, accidentally, allow the browser to remember the password. In addition, federated authentication makes this even easier to leave yourself logged in.

I’d like to make a bold statement;

The level of knowledge a person is required to have, right now, to be secure using modern technology such as web applications, is higher than even normal IT-literate users currently have.

I’ll give you an example. If you use federated authentication, then you may end up logged in to both what you expected to be logged in to and the authentication provider. E.g.. log in to (just an example) by clicking the G button and put in your Google credentials. Now log out of Clarizen. You would think you were logged out - not so. Now go to See that you are also logged in to Google. Did you realise that before now? I bet you did not.

The mistake that Clarizen are making is that they failed to realise that users expect single-sign-on and but also single-sign-off. The mistake users are making is not realising that single-sign-on does not mean single-sign-off.

The solution for Clarizen and others is to make their log out link redirect to the Google (or other) log out URL. I have recently used this technique with great success with an integration project. Naturally you will want to warn the user that it will do a full log out.

The solution for users, including me, is to always always always use an Incognito Window. Never log on to another user’s computer without using one. What this does is ensure that nothing gets saved on the computer (except downloads) - even if you accidentally allow it to remember passwords or save authorisation on the computer. Once you close the incognito window, all traces that you were there, cookies, passwords, user names, history, etc, are gone.

Incognito also allows you to browse knowing that there will be no history so that if you are looking for something online that you would not like your partner to see, your secret is safe. (I am thinking presents...).

Incognito is available in:
  • Google Chrome - Tool menu > New incognito window
  • FireFox 4 - Tools > Start Private Browsing (Ctrl+Shift+P)
  • Internet Explorer 9 - Cog menu > Safety > InPrivate Browsing
  • Safari - Edit menu > Private Browsing
  • Opera - Menu > Private Tab / Private Window
Remember though, it is only going to ensure nothing is left on the computer. If the computer is infected with a key logger and you’re not using two factor authentication, then your account is screwed anyway. Also, if the network admin is using a good web filter, such as Smoothwall Network Guardian, then he will know exactly where you’ve been - even if you tried to hide it.

More info can be found on this Wikipedia article.


  1. Nice article. I often wondered if incognito had a use outside obsessive self abuse ;)

    Moral of the story - opposite "ideas" should be symmetric.. logging in should be entirely the opposite of logging out - ie the logout button should undo everything the login button does. Otherwise users are left having to remember the difference.

  2. Zendesk also suffers the security hole of lack of single-sign-out I discovered today.