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A Defcon survival guide

How to surf in a hostile environment and live to tell the tale

Beginner's guide to SSL certificates

Defcon It's almost time for Defcon, the most bacchanal of security conferences and perhaps the single largest gathering of technically adept pranksters. Now is the perfect time to map out a strategy for keeping emails private and making sure your system doesn't get ransacked by the scowling kid with the nose ring and jet-black hair.

It only takes a single weakness to be penetrated, so the only way to be sure you won't get hacked is to leave your computer at home, or short of that, not to plug in to the wireless network there. This may sound extreme, but it's the truth. If your only need for a machine while at the show is to check sports scores, consider going without.

OK, so what about the rest of us? Good security is no accident, so make a plan of action for the way you'll access your email or connect to sensitive work servers.

Before you go:

  • Make sure your system is fully patched, no matter what operating system you're running. Those running Linux, make sure your kernel is current.
  • Back up all important data and then remove all private information that you can do without at the conference.

Once at the conference, think of ways to minimize the attack surface of your machine by removing all non-essential services.

  • In Windows, turn off Client for Microsoft Networks, File and Printer Sharing and NetBIOS over TCP/IP. (The first two are done by accessing Control Panel > Network Connections > Wireless Network Connection and choosing Properties. Uncheck the two boxes. With the properties window still open, highlight Internet Protocol TCP/IP and choose properties >Advanced > Wins and select Disable NetBIOS over TCP/IP.
  • Whether you use Windows' built-in firewall or a stand-alone one, disable all exceptions that you won't need while at the show.
  • If you've brought a Mac, good for you, but don't think you're impenetrable. Check your System Preferences to make sure services such as Personal Filesharing, Windows Sharing, and Remote Login are turned off in the Sharing panel.
  • If you're running iTunes on either a Mac or a PC, make sure the Looked for Shared Libraries and Share my library on my local network boxes are unchecked. We've never trusted the Bonjour service Apple uses to enable this feature, and Defcon would be the perfect place to exploit an overlooked vulnerability in it.
  • It's almost inevitable that someone will try to poison the Defcon DNS. Hardwiring one into your machine's network settings can circumvent some attacks, although not those that use spoofing. (In Windows, it's Control Panel > Network Connections > Wireless Network Connection > Properties >Internet Protocol (TCP/IP) > Properties and select Use the follow DNS server automatically.) We're partial to OpenDNS, whose addresses are 208.67.222.222 and 208.67.220.220.
  • Traffic traveling over any public Wi-Fi is easily intercepted. Remember, you don't want to wind up on the Wall of Sheep. Never, ever transmit a password or other piece of personal information in the clear.
  • If you can, use an industrial-strength VPN that secures email and access to your company servers. If you don't have one, see if you have ssh access to a machine outside of the conference. (e.g. ssh -D 6666 user@my.university.server.edu).
  • If neither of the above work, make sure to only access email and initiate sensitive connections using SSL connections, such as https://gmail.com. The customizegoogle firefox extension has a setting to ensure traffic for gmail, Google Calendar and Google Docs always uses SSL.
  • Most of the IM clients use an unencrypted link to send data, including login credentials, so don't use IM at Defcon.

Finally, remain vigilant and expect the unexpected. As one SANS diary writer put it a couple years ago: "try to recall all of the attacks you have seen in the last year and dismissed because the attacker needed to be local to your network. Then realize that you are about to to connect to that network."

Beware of fake access points and rogue DHCP servers. If you haven't already done so, install the NoScript Firefox extension. While at Defcon, don't install any updates for any software.

Our thanks to Chris Soghoian for help in compiling this collection of best practices. It's by no means complete, and we invite our readers to share additional measures security mongers can take to lock down their machines. We're also happy to try our hand at answering questions. ®

Protecting users from Firesheep and other Sidejacking attacks with SSL

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