If you're new to the Linux or open source community, you might not have heard of live disc or USB distributions yet. They let you run a operating system on PCs without installing anything on the hard drive. It loads directly from the CD/DVD disc or USB flash drive. Many full Linux desktop distros, such as Ubuntu, can be ran in this live mode. However, there are also live distros created for a wide-variety of other specific applications and solutions. Here we'll review several of these. Let's get started!

Public IP ZoneCD: hotspot gateway

This turns a PC into a hotspot gateway, helping you offer public wireless Internet while protecting your private network. The PC you use can be a old, slow, machine. You just need a minimum 128 MB of RAM, bootable CD-ROM, floppy drive or USB flash drive, and two Ethernet cards. You will also need at least one router (wired or wireless) and a wireless access point (or another wireless router). The Live CD machine will sit between these two components.

You don't need to be a Linux user to configure or manage the system; its pretty user-friendly. The free service provides all the basic hotspot functionality: captive portal, content filtering, bandwidth throttling, walled garden, and firewalling. Premium services give you even more features, such as a ticketing system, printer support, and captive portal customization.

Linux LiveCD Router: wireless router, firewall, and internet connection balancing

This turns your computer into a router, firewall, and load balancer. It requires only 32 MBs of RAM, a CD-ROM drive or USB flash disk, and one or more Ethernet cards. The free version is command-line based. The professional edition runs at $149 and includes the GUI or web-based interface, site-to-site VPN, and more.

If you have a supported Wi-Fi card, you can offer wireless access, turning it into a wireless router. If you have multiple Internet connections, it can balance their usage and provides backup in case one line goes down.

The Linux LiveCD Router supports ADSL, cable, 3G, T1, dial-up, and Wi-Fi Internet connections. It does traffic shaping with its quality of service (QoS) settings. It also features remote SSH administration and OpenVPN.

BackTrack: network security, penetration, and forensics tools

BackTrack is a Linux desktop distro dedicated to network security, penetration testing, and forensics. It comes preloaded with many different analyzers, scanners, and drivers. You might use it to see how easy it is to crack WEP or WPA/WAP2-PSK encryption. You could also use it to monitor employees or find holes in your security perimeter.

Wireshark is included, which is a general purpose network sniffer or analyzer displaying the raw network packets. Kismet can serve as your wireless network detector and analyzer, giving you the ability to see the SSID or network name of  "hidden" networks. Nmap (Network MAPper) can be your security scanner, helping you discover hosts and services on networks. Ettercap lets you do snooping on many protocols, for instance, to collect passwords. This is just a few of the tools; there are many more.

Knoppix: general purpose

This is actually one of the first live CDs that become available, which is a Debian-based Linux distribution. It can serve as a general purpose desktop OS on CD, USB, or installed onto your hard drive. However, it can also serve as a recovery tool, for example, letting you access drives when Windows is inaccessible.

Thousands of open source and proprietary applications are included with Knoppix, more of which are included in the DVD versus the CD version. OpenOffice.org gives you a comprehensive office suite, compatible with MS Office. You'll have a web browser, media player, image programs, rescue and repair utilities, network tools, and much more.

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