* Don't run unnecessary services (called "daemons" in UNIX) that allow internet connections - some distributions turn these on by default. Examples are mail or news servers and printer daemon (lpd). If you want to see a list of the daemons running on your machine, at a command prompt type:%%% netstat -apAinet%%%(You'll need to do this as "root" to get all process information). The lines that say "LISTEN" means a daemon is waiting for connections on the specified TCP port. Don't forget to check your UDP ports too - all sorts of things can lurk there. 

  

 * Firewall your machine using iptables(8) (or possibly ipchains(8) or even ipfwadm(8) if you're on an older machine). Don't just deny that which you know you don't want - deny everything, then specifically allow what you want to be let in. 

  

 !Application / General Encryption 

 GNU Privacy Guard ([GPG]) is an encryption program compatible with Pretty Good Privacy ([PGP]). It uses public-key cryptography, and many email clients have hooks that allow you to fairly easily encrypt and "sign" email. See our [GPG/PGPNotes] page. 

  

 !Wireless Network Security: 

 See WirelessNetworkSecurityNotes