The Register has an interesting article on how to "safely" take your computer to Defcon, with the very wise suggestion that you're safer if your laptop does not go to Defcon. Cellular phones without 802.11 are probably okay for this year at least. They refer back to a much more hard-core SANS post on the same topic.

The exercise is more involved for the fully paranoid, or generally when preparing to enter a truly hostile network. I assume that someone at Black Hat/Defcon has an unannounced exploit that I'd be vulnerable to. This implies you shouldn't have any sensitive data or access to sensitive machines. Since you wouldn't need a laptop without data or access, you probably need to mitigate the consequences of getting hacked.

  1. Make up a couple disposable passwords just to use at the conference, one for this machine and one for outside accounts. Destroy them later.
  2. Bring an empty USB thumb drive.
  3. Create a new email account, so you can send yourself notes/presentations for later.
  4. Forward your important email accounts to the new one (keep copies on the normal accounts), so you don't have to check them.
  5. Note that if you have a hosting plan like DreamHost's, you can create brand-new ssh and email accounts free. I believe DH offers SSL webmail, if you can ignore the certificate warnings.
  6. Get a cheap monthly VPN account, as suggested by Glenn Fleishmann; this is much simpler than establishing a trusted Squid proxy on a non-sensitive box, as originally suggested by SANS; note that you are then trusting the VPN provider.
  7. If you have any untrusted protocols, try to access them from your temporary shell account via ssh, or though an ssh tunnel.
  8. Back up your data (image the drive -- you will need it later, and a full image is fastest to restore).
  9. Wipe your laptop.
  10. Install your OS, creating a new account with your new local password.
  11. If you have a built-in webcam with an independently software-controlled active light, tape over it. If you feel comfortable opening up your laptop, disconnect its internal microphone.
  12. Create a new ssh keypair. If you know the netblock, only allow access from Defcon machines and your own personal host(s); I have some info on doing this in authorized_keys in Take Control of SSH, Draft Excerpt: Public Key Authentication. Make sure your laptop trusts your other (home) machines.
  13. Only as needed, trust this new key on your other systems.
  14. In your local firewall, block outbound access except to the ports you intend to use; this is easy in Linux, but a bit more complicated on Macs, where you need to write your own startup script (or .command script in Login Items). This is obviously overridable, but an effective way to make sure you don't accidentally connect without encryption, either from habit or because a website redirects you to unencrypted HTTP to save encryption cycles (common). For services where you know what host you'll be connecting to, embed that. Here's a sample of what you might add to add Apple's ipfw. Note that it's easy to shoot your own foot off with outbound firewall restrictions.

    ipfw add 01010 allow tcp from any to dst-port 53 out
    ipfw add 01020 allow udp from any to dst-port 53 out
    ipfw add 01030 allow tcp from any to dst-port 53 out
    ipfw add 01040 allow udp from any to dst-port 53 out
    ipfw add 01110 allow tcp from any to any dst-port 22 out
    ipfw add 01120 allow tcp from any to any dst-port 443 out
    ipfw add 01030 allow tcp from any to dst-port 587 out
    ipfw add 01040 allow tcp from any to dst-port 993 out
    ipfw add 01900 deny tcp from any to any out
  15. Restore only required information to your laptop.

Enjoy the conference. Hi, Rich!

When you're back home, connect from your home machines to the untrusted laptop, rather than the other way around, retrieve any data on it, and then boot from CD/DVD/PXE and reinstall, or restore from your image if you can do that without using the untrusted OS on the laptop's hard drive.