When using a network of any kind (public, private, wifi, tethered) you need to be aware that the info you are pushing around the network(s) is prone to snooping, sniping and prying eyes. Proper use of some apps can limit the amount of information that gets leaked across the inter, and intra, tubes.
Encryption - this is the act of turning your clear text info into encrypted bundles that can only be read by the intended recipients.
- A simple way of using this is to make sure the web sites you are passing information thru use a secure transport. You can often tell this by noting the URL begins with https rather then http. You can also check the bottom bar of your browser and see if the lock icon is open or closed. Read up on your browsers particular method of reporting whether you are using a secure method or not.
For email and other message passing services you can use GnuPG which is the GNU project's complete and free implementation of the OpenPGP standard. GnuPG allows to encrypt and sign your data and communication, features a versatile key managment system as well as access modules for all kind of public key directories. You can find ourt all about it on their website...http://www.gnupg.org/
There are several ways to integrate GPG into the ways you like to send email. If you use gmail you can use the firefox addon called FireGPG ( http://getfiregpg.org/ ), this makes it a breeze to sign and encrypt, as well as decrypt , all your email.
Anonymity - or "Hiding Your Movements" - this is the act of not allowing governments, data mining companies or just run of the mill packet snoop from easily seeing what places you are going to on the internet.
A popular tool for doing this is TOR (http://www.torproject.org/). After setting it up your traffic is moved thru a complicated and , hopefully, baroque enough twisty encrypted path that most snooping agencies will not be able to follow you about and glean information from your travels.
There are several tools that make using Tor much easier. One is Tork ( http://www.anonymityanywhere.com/tork/ ) Tork is a GUI manager for Tor that helps you install, configure and use Tor. It reduces the task of anonymizing most applications to a single-click, including Firefox, Opera,Konqueror,Pidgin, Kopete,SSH, and IRC.For advanced users TorK provides detailed network information, and more, in an accessible manner. Torks is a tad KDE centric.
Vidalia ( http://vidalia-project.net/ ) on the other hand, is a cross-platform GUI manager for Tor. You can start and stop the Tor software, view its status at a glance, and monitor bandwidth usage. Vidalia also makes it easy to contribute to the Tor network by helping you set up and manage your own relay.
Some apps you may alredy be using can benefit from using Tor. Xchat, for instance, can be made to use Tor on most any irc network that allows it. Freenode has a special Tor entry ( http://freenode.net/irc_servers.shtml) and the PTP Irc server currently accepts connections for the Tor network.
One Stop Shopping - there are several projects that are crafting easy to run LiveCD based Operating Systems that will offer you many of the apps mentioned above built into a full fledged linux desktop system. The benefit of these are they can be run from any computer that has a CD/DVD drive or even a USB port. Say for instance that you are visiting a local cafe that has several public computers, you can simply reboot the machines with the LiveCD inserted and it would boot up into a secure desktop environment.
Incognito - http://www.browseanonymouslyanywhere.com/incognito - "This CD provides software to use various Internet technologies while keeping the user anonymous. It is based primarily on Tor while including supporting applications. The target use case is that of using a public computer, such as in a library, securely. This CD may also be copied to a USB drive to provide persisted user settings. The intended user base are those who would like to perform standard Internet communications such as WWW, mail, IRC, IM, etc, while being confident that their anonymity is not compromised. Power users who want precise control over the application and network configuration may be disappointed. " This distro is Gentoo and KDE based.
ParanoidLinux - http://paranoidlinux.org/ - Still very much in the alpha stages ParanoidLinux has very similar aims as Incognito with several exceptions/additions. It is based around Ubunutu and Gnome.