Skip to content

Posts tagged ‘cookies’

25
Oct

Intercepting Unencrypted Sessions with Firesheep

Firesheep, a new Firefox extension that allows you to intercept unencrypted sessions being transmitted over the network, has been released by Eric Butler. Taking advantage of websites that don’t use SSL by default, such as Facebook and Twitter, Firesheep uses network-sniffing to intercept the cookies used to transport session IDs (also known as sidejacking). Note this attack will work over Wifi by default, but will require extra work on a switched wired network.

Once Firesheep has intercepted a user’s cookie over the network, it allows you to be logged in as that user. The concept of session-stealing is as old as the internet, but to have a Firefox extension that does it in such a user-friendly manner is great. It’s also a lot more dangerous as it makes this attack so much easier for any unskilled attacker to carry out.

Firesheep Screenshot

Protecting Yourself

The are a couple ways of protecting yourself from sidejacking attacks.  The first and foremost is to ensure that you use SSL when visiting popular or particularly sensitive web services, including Gmail, Hotmail, Facebook, Twitter, or any other site that’s of importance to you (online banking?). The best way of doing this is to make sure your bookmarks (or the URL you type in) starts with “https://”, and that no SSL certificate errors appear. Another Firefox plugin, HTTPS Everywhere, from the privacy advocates over at the Electronic Frontier Foundation (EFF), enforces SSL on predefined sites. You can also protect your searches by using Google over SSL (encrypted.google.com).

Another way of protecting yourself is to channel your browser traffic through a VPN or SSH Tunnel. Your data is then sent through an encrypted link to a remote host (preferably one you control), before being sent to the destination.

Installing Firecat

Firebug runs in Firefox on Mac OS X and Windows, however Windows users will need to install WinPcap first. After downloading the extension file (xpi), simply open it by going to File -> Open File (you will need to restart Firefox). To clarify some confusion, once you’ve installed the extension, you need to go to View -> Sidebar -> Firesheep to enable it, and click Start Capturing.

Give it a try for yourself.

[Update] Detecting and protecting against Firesheep with FireShepherd.

19
Oct

Persistent Tracking using Supercookies and Evercookies

Normal websites use cookies to keep track of their visitors, either to remember that they are logged in, track statistics, or a number of other purposes. Sites can usually only track users while they are browsing that actual site (apart from Google who tracks you more or less wherever you go), however the past few years have revealed more and more ways web users can be tracked.

The concept of supercookies and ubercookies is not entirely new, but has been refined recently to turn them into digital cockroaches – very hard to permanently get rid of. Supercookies are basically an amalgamation of different software features that can be used to create a uniquely identifying token, usually one that is hard or too convoluted to delete. Now that HTML5 is becoming more widespread, there are even more options than before.

Modern supercookies comprise a number (or all) of the following:

  • Standard HTTP Cookies
  • Local Shared Objects (Flash Cookies)
  • Silverlight Isolated Storage
  • Storing cookies in RGB values of auto-generated, force-cached PNGs using HTML5 Canvas tag to read pixels (cookies) back out
  • Storing cookies in Web History
  • Storing cookies in HTTP ETags
  • Storing cookies in Web cache
  • window.name caching
  • Internet Explorer userData storage
  • HTML5 Session Storage
  • HTML5 Local Storage
  • HTML5 Global Storage
  • HTML5 Database Storage via SQLite

Samy Kamkar recently released Evercookie, a JavaScript API for creating extremely persistent browser cookies. The list above is what is what Evercookie uses to create them. If websites were to start using these techniques, they would be able to uniquely identify you (as a user, not a person) each time you visited, even if you deleted your cookies, cleared your cache, and removed your history (or used a private browsing feature). Due to the use of shared objects, such as Flash, some cookies are persistent even across different browsers!

Ultimately, I wouldn’t panic and stop surfing the web just yet, but this goes to show how the evolution of the browser (and countless plugins that now go with it) is having an effect on privacy and security (which can’t quite keep up the pace set by innovation). Dominic White describes how to delete the Evercookie when using Safari on OSX. Others have written about how to do the same on Firefox and Chrome. One reddit user has created a pseudo lockdown-script which improves the security and privacy of Firefox by making some configuration changes (eg. disabling prefetching, geolocation, caching, etc).

This post by Christopher Soghoian provides a good argument for why privacy (and security, I would add) should be adopted in web browsers by default, instead of letting users fend for themselves. Some browsers are making an effort by adding features such as private browsing, cross-site scripting protection, and Google SafeSearch (although this impacts privacy by sending Google every URL you browse to), however all too often browser plugins and add-ons are given too many privileges.

Browser security and user awareness are becoming more important than ever as traditional programs are phased out and replaced by web applications. Unfortunately both of these are still lagging a bit behind.

css.php